Effect of large conductance Ca2+-activated K+ channel current and cytosolic calcium concentrations in retinal artery smooth muscle cells on diabetic retinal artery tension / 中华实验眼科杂志

Background Diabetic retinopathy (DR) is a common microvascular complications of the retina,retinal vascular smooth muscle cells of large conductance calcium-activated potassium channels (BK) is a major factor in regulating vasomotor and hemodynamic.Currently,functional changes of BK channel in retinal artery smooth muscle cells (RASMCs) and its role in DR were rarely reported.Objective This study was to investigate the early vascular damage mechanisms in DR by detecting the changes of BK channels current,calcium concentration and open probability (NP0) of BK channel with different calcium concentration in RASMCs of normal and diabetic rats.Method Fifty SPF SD 8-12 weeks old rats were randomly divided into normal control group and diabetic model group.Forty diabetic rats was intraperitoneally injected with 60 mg/kg streptozotocin to form type 1 diabetic model,10 rats (the normal control group) were injected sodium citrate solution with the same manner.Fluorescent probe was applied to detect calcium concentration in rat RASMCs;RASMCs were isolated by using enzyme digestion,and BK-channel electric currents and calcium concentrations in the RASMCs were measured by whole-cell patch clamp technique and fluorescence assay,respectively.The NP0 of BK channel was measured by single patch clamp technique.Results Diabetic models were successfully established in 36 rats with the success rate 90％.When stimulation voltage is greater than 60 mV,the current density of BK channel in RASMCs of diabetic model group decreased;when stimulating voltage was 100 mV,the BK channel currents of RASMCs in the normal control group and diabetic model group were (100±23) PA/PF and (50 ± 7) PA/PF,the difference was statistically significant (t =19.80,P ＜ 0.05).After adding specific BK channel blocker African scorpion toxin 100 nmol,the BK channel current in the normal control group significantly reduced,and that in the diabetes model group was not significantly changed;the calcium ion concentrations in RASMCs were (123±11)nmol/L and (255± 10)nmol/L in the normal control group and diabetic model group,the difference was statistically significant (t =32.50,P＜0.05).When stimulation voltage was 60 mV,with increasing calcium ion concentration,the NP0 of BK channel increased (F =15.28,P＜0.05).Conclusions The electric current and NP0 of BK-channel are obviously reduced and the calcium concentration is evidently elevated in RASMCs of diabetic rats,suggesting that the abnormal of BK-channel is probably one of the important causes of retinal artery abnormal contraction in diabetic rats.

Effect of ropivacaine combined with pancuronium on neuromuscular transmission and effectiveness of neostigmine and 4-aminopyridine for blockade reversal: experimental study / Efeito da associação ropivacaina-pancurônio na transmissão neuromuscular e eficácia da neostigmine e 4-aminopiridina na reversão do bloqueio: estudo experimental / Efecto de la asociación ropivacaína-pancuronio en la transmisión neuromuscular. Eficacia de la neostigmina y 4-aminopiridina en la reversión del bloqueo. Estudio experimental

BACKGROUND AND OBJECTIVES: The local anesthetic effects on neuromuscular junction and its influence on blockade produced by nondepolarizing neuromuscular blockers are still under-investigated; however, this interaction has been described in experimental studies and in humans. The aim of this study was to evaluate in vitro the interaction between ropivacaine and pancuronium, the influence on transmission and neuromuscular blockade, and the effectiveness of neostigmine and 4-aminopyridine to reverse the blockade. METHODS: Rats were divided into groups (n = 5) according to the study drug: ropivacaine (5 µg mL-1); pancuronium (2 µg mL-1); ropivacaine + pancuronium. Neostigmine and 4-aminopyridine were used at concentrations of 2 µg mL-1 and 20 µg mL-1, respectively. The effects of ropivacaine on membrane potential and miniature endplate potential, the amplitude of diaphragm responses before and 60 min after the addition of ropivacaine (degree of neuromuscular blockade with pancuronium and with the association of pancuronium-ropivacaine), and the effectiveness of neostigmine and 4-aminopyridine on neuromuscular block reversal were evaluated. RESULTS: Ropivacaine did not alter the amplitude of muscle response (the membrane potential), but decreased the frequency and amplitude of the miniature endplate potential. Pancuronium blockade was potentiated by ropivacaine, and partially and fully reversed by neostigmine and 4-aminopyridine, respectively. CONCLUSIONS: Ropivacaine increased the neuromuscular block produced by pancuronium. The complete antagonism with 4-aminopyridine suggests presynaptic action of ropivacaine. .

JUSTIFICATIVA E OBJETIVOS: Os efeitos dos anestésicos locais na junção neuromuscular e sua influência no bloqueio produzido por bloqueadores neuromusculares não-despolarizantes é ainda alvo de pouca investigação, no entanto esta interação tem sido descrita em trabalhos experimentais e em humanos. O objetivo deste estudo foi avaliar in vitro, a interação da ropivacaína com o pancurônio, a influência na transmissão e bloqueio neuromuscular e a efetividade da neostigmina e 4-aminopiridina na reversão do bloqueio. MÉTODO: Ratos foram distribuídos em grupos (n = 5) de acordo com o fármaco estudado: ropivacaína (5 µg mL-1); pancurônio (2 µg mL-1); ropivacaína + pancurônio. A neostigmina e a 4-aminopiridina foram usadas nas concentrações de 2 µg mL-1 e 20 µg.mL-1, respectivamente. Avaliou-se: 1) efeitos da ropivacaína sobre o potencial de membrana e potenciais de placa terminal em miniatura; 2) a amplitude das respostas do diafragma antes e 60 minutos após a adição da ropivacaína; o grau de bloqueio neuromuscular com o pancurônio e com a associação pancurônio - ropivacaína; 3) a efetividade da neostigmina e 4-aminopiridina na reversão do bloqueio neuromuscular. RESULTADOS: A ropivacaína não alterou a amplitude das respostas musculares, os potenciais de membrana, mas diminuiu a frequência e a amplitude dos potenciais de placa terminal em miniatura. O bloqueio produzido pelo pancurônio foi potencializado pela ropivacaína, e parcial e totalmente revertido pela neostigmina e 4-aminopiridina, respectivamente. CONCLUSÕES: A ropivacaína potencializou o bloqueio neuromuscular produzido pelo pancurônio. O antagonismo completo com a 4-aminopiridina sugere ação pré-sináptica da ropivacaína. .

JUSTIFICACIÓN Y OBJETIVOS: Los efectos de los anestésicos locales en la unión neuromuscular y su influencia en el bloqueo producido por bloqueantes neuromusculares no-despolarizantes todavía son poco investigados, sin embargo, esta interacción ha sido descrita en trabajos experimentales y en seres humanos. El objetivo de este estudio fue evaluar in vitro la interacción de la ropivacaína con el pancuronio, la influencia en la transmisión y bloqueo neuromuscular y la efectividad de la neostigmina y 4-aminopiridina en la reversión del bloqueo. MÉTODO: Unos ratones fueron distribuidos en grupos (n = 5) de acuerdo con el fármaco estudiado: ropivacaína (5 µg/ml-1); pancuronio (2 µg/ml-1); ropivacaína + pancuronio. La neostigmina y la 4-aminopiridina fueron usadas en concentraciones de 2 µg/ml-1 y 20 µg/ml-1, respectivamente. Evaluamos: 1) efectos de la ropivacaína sobre el potencial de membrana y potenciales de placa terminal en miniatura; 2) la amplitud de las respuestas del diafragma antes y 60 min después de la adición de la ropivacaína; el grado de bloqueo neuromuscular con el pancuronio y con la asociación pancuronio-ropivacaína; 3) la efectividad de la neostigmina y 4-aminopiridina en la reversión del bloqueo neuromuscular. RESULTADOS: La ropivacaína no alteró la amplitud de las respuestas musculares, los potenciales de membrana, pero disminuyó la frecuencia y la amplitud de los potenciales de placa terminal en miniatura. El bloqueo producido por el pancuronio fue potenciado por la ropivacaína, y parcial y totalmente revertido por la neostigmina y 4-aminopiridina, respectivamente. CONCLUSIONES: La ropivacaína potenció el bloqueo neuromuscular producido por el pancuronio. El antagonismo completo con la 4-aminopiridina muestra una acción presináptica de la ropivacaína. .

In vitro and in vivo neuromuscular effects of atracurium and rocuronium in rats treated with carbamazepine for seven days / Efeitos neuromusculares in vitro e in vivo do atracúrio e do rocurônio em ratos submetidos a tratamento de sete dias com carbamazepina / Efectos neuromusculares in vitro e in vivo del atracurio y del rocuronio en ratones sometidos a tratamiento de siete días con carbamazepina

JUSTIFICATIVA E OBJETIVOS: Trata-se de um estudo experimental que investigou in vitro e in vivo o bloqueio neuromuscular produzido pelo rocurônio e atracúrio em ratos tratados com carbamazepina e determinou as concentrações de citocromo P450 e b5 redutase em microssomos hepáticos. MÉTODO: Ratos foram tratados por sete dias com carbamazepina (CBZ) - 40 mg.kg-1 pelo método de gavagem e sacrificados no oitavo dia sob anestesia com uretana. As preparações in vitro e in vivo foram montadas de acordo com as técnicas de Bulbring e de Leeuwin e Wolters, respectivamente. As concentrações e doses utilizadas dos bloqueadores nas preparações in vitro e in vivo foram, respectivamente, 20 µg.mL-1 e 0,5 mg.kg-1 para atracúrio (ATC); 4 µg.mL-1 e 0,6 mg.kg-1 para rocurônio (ROC). Cada protocolo teve um n = 5 e as respostas foram observadas por 60 minutos. Os efeitos do ATC e ROC foram avaliados nas preparações de ratos tratados (Cbz t) e comparados com os observados nas de ratos não-tratados (CBZst). As concentrações de citocromo P450 e b5 redutase foram determinadas em microssomos isolados de fígados de ratos tratados (CBZt) e comparadas com as obtidas em ratos não tratados (CBZst). RESULTADOS: A carbamazepina não alterou a amplitude das respostas musculares; in vitro e in vivo, não houve diferença entre o bloqueio neuromuscular produzido pelo atracúrio nas preparações CBZt versus CBZst; o bloqueio neuromuscular produzido pelo rocurônio nas preparações CBZt foi potencializado in vitro. A carbamazepina não alterou as concentrações de citocromo P450 e b5. CONCLUSÕES: O tratamento por sete dias com carbamazepina não influenciou no bloqueio produzido pelo atracúrio, e alterou in vitro os efeitos do rocurônio. O tempo de tratamento não foi suficiente para causar indução enzimática e diminuir a sensibilidade ao rocurônio.

BACKGROUND AND OBJECTIVES: This experimental study investigated the in vitro and in vivo neuromuscular blockade of rocuronium and atracurium in rats treated with carbamazepine and determined the concentration of cytochrome P450 and b5 reductase in hepatic microsomes. METHODS: Rats were treated with carbamazepine (CBZ) - 40 mg.kg-1 by gavage and sacrificed on the eighth day under anesthesia with urethane. In vitro and in vivo preparations followed the techniques of Bulbring and Leeuwin and Wolters, respectively. Concentrations and doses of the neuromuscular blockers used in in vitro and in vivo preparations were, respectively, 20 µg.mL-1 and 0.5 mg.kg-1 for atracurium (ATC); and 4 µg.kg-1 and 0.6 mg.kg-1 for rocuronium (ROC). Each protocol had an n = 5 and the response was observed for 60 minutes. The effects of ATC and ROC were evaluated in the preparations of rats treated with carbamazepine (CBZt) and compared to those of non-treated rats (CBZst). The concentration of cytochrome P450 and b5 reductase were determined in hepatic chromosomes of rats treated with carbamazepine (CBZt) and non-treated rats (CBZst). RESULTS: Carbamazepine did not change the amplitude of neuromuscular response; differences in the neuromuscular blockade produced by atracurium in CBZ1 preparations were not observed, in vitro or in vivo, when compared with CBZst; the neuromuscular blockade produced by rocuronium in CBZt preparations was potentiated in vitro. Carbamazepine did not change the concentrations of cytochrome P450 and b5. CONCLUSIONS: Seven-day treatment with carbamazepine did not change the neuromuscular blockade produce by atracurium, but altered the in vitro effects of rocuronium. The duration of the treatment was not enough to cause enzymatic induction and decrease the sensitivity to rocuronium.

JUSTIFICATIVA Y OBJETIVOS: Se trata de un estudio experimental que investigó in vitro e in vivo el bloqueo neuromuscular producido por el rocuronio y atracurio en ratones tratados con carbamazepina y determinó las concentraciones de citocromo P450 y b5 reductasis en microsomas hepáticos. MÉTODO: Ratones fueron tratados por siete días con carbamazepina (CBZ) - 40 mg.kg-1 a través de una sonda y sacrificados al octavo día bajo anestesia con uretana. Las preparaciones in vitro e in vivo fueron montadas de acuerdo con las técnicas de Bulbring y de Leeuwin y Wolters, respectivamente. Las concentraciones y dosis utilizadas de los bloqueadores en las preparaciones in vitro e in vivo fueron, respectivamente, 20 µg.mL-1 y 0,5 mg.kg-1 para atracurio (ATC); 4 µg.mL-1 y 0,6 mg.kg-1 para rocuronio (ROC). Cada protocolo tuvo un n = 5 y las respuestas fueron observadas por 60 minutos. Los efectos del ATC y ROC fueron evaluados en las preparaciones de ratones tratados (Cbz t) y comparados a los observados en los de ratones no tratados (CBZst). Las concentraciones de citocromo P450 y b5 reductasis fueron determinadas en microsomas aislados de hígados de ratones tratados (CBZt) y comparadas con las obtenidas en ratones no tratados (CBZst) RESULTADOS: La carbamazepina no alteró la amplitud de las respuestas musculares; in vitro y in vivo, no hubo diferencia entre el bloqueo neuromuscular producido por el atracurio en las preparaciones CBZt versus CBZst; el bloqueo neuromuscular producido por el Rocuronio en las preparaciones CBZt fue potenciado in vitro. La carbamazepina no alteró las concentraciones de citocromo P450 y b5. CONCLUSIONES: El tratamiento por siete días con carbamazepina, no influenció en el bloqueo producido por el atracurio, y alteró in vitro los efectos del rocuronio. El tiempo de tratamiento no fue suficiente para causar la inducción enzimática y disminuir la sensibilidad al rocuronio.

Unilateral Cervical Sympathectomy Attenuates Hypertensive Responses Induced by Intracerebroventricular Administration of Choline in Rats / 대한마취과학회지

BACKGROUND: Brain acetylcholine is an important neurotransmitter in the control of blood pressure. Pharmacological activation of central cholinergic receptors by intracerebroventricular (ICV) administration of choline resulted in a marked pressure response in hypotensive experimental models, and the pressure response was associated with an increase in plasma vasopressin levels. The aim of this study was to determine whether a unilateral cervical sympathectomy affects the pressure response induced by ICV choline. METHODS: Rats were prepared with a cervical sympathectomy or with a sham operation and a 23 G cannula was implanted into the lateral cerebral ventricle. They were divided into three groups according to the pre-treated condition and the solution injected into the lateral cerebral ventricle; group 1 (ICV saline after sham operation), group 2 (ICV choline after sham operation), group 3 (ICV choline after cervical sympathectomy). Following the recovery period, pressure response was monitored for 50 min after injecting ICV choline or saline and plasma vasopressin levels were also assessed with an EIA kit at preinjection time, 10 min, and 50 min after ICV injection. RESULTS: The baseline systolic blood pressure was 120.6 +/- 3.9 mmHg in group 3 and 121.7 +/- 9.0 mmHg in group 2 and there was no significant difference. The pressure response to ICV choline became evident within 1 min and reached a maximum magnitude in 10 min in both groups. Compared to the sham operated rats (group 2), the pressure response to ICV choline was significantly attenuated in sympathectomized rats (p < 0.05). However, the plasma vasopressin levels were not significantly affected by ICV choline or a cervical sympathectomy. CONCLUSIONS: While the unilateral cervical sympathectomy itself did not have any effect on bloodpressure, it attenuated the pressure response to ICV choline. A unilateral cervical sympathectomy may attenuate the hypertensive response which is caused by an increased central cholinergic neurotransmission.

The Mechanism of Antiallodynic Effect of Intrathecal Morphine in Neuropathic Pain Induced by Spinal Nerve Ligation / 대한마취과학회지

BACKGROUND: Although the efficacy of morphine in a neuropathic pain state is somewhat controversial, intrathecally administered morphine reversed the mechanical allodynia in a previous animal study. Using a behavioral test, we investigated the mechanism of the antiallodynic action of intrathecal morphine by administering opioids, alpha2 adrenergic and cholinergic receptor antagonists in a rat model of neuropathic pain induced by a spinal nerve ligation injury. METHODS: Male Sprague Dawley rats were prepared with a tight ligation of the left lumbar 5th and 6th spinal nerves and insertion of a chronic lumbar intrathecal catheter. Morphine 1 microgram was administered intrathecally to attenuate the mechanical allodynia. Naloxone 10 microgram, yohimbine 30 microgram, prazosin 30 microgram, atropine 10 microgram, pirenzepine 10 microgram, and methoctramine 10 microgram was administered intrathecally before and after the injection of morphine in order to investigate the reversal of an increased allodynic threshold by morphine. The allodynic thresholds for the left hindpaw withdrawal to von Frey hairs were assessed and converted to %MPE. RESULTS: A reduction of mechanical allodynia by intrathecal morphine was produced. Naloxone pretreatment, but not posttreatment, reversed the antiallodynic effect of intrathecal morphine (P < 0.01). All alpha2 adrenergic and cholinergic receptor antagonists used here did not reverse it. CONCLUSIONS: The results suggest that the reversal mechanism of mechanical allodynia by intrathecal morphine appears to be mediated mostly by the opioid receptor system, but not the alpha2 adrenergic and cholinergic receptor systems, at the spinal level in a rat model of a spinal nerve ligation injury.

The Value of Systemic Ketamine for Preemptive Analgesia in a Rat Model for ostoperative Pain / 대한마취과학회지

BACKGROUND: Pretreatment of systemic ketamine reduced pain behaviors in some animal models with persistent pain. However, a clinically relevant preemptive analgeisic effect of systemic ketamine is controversial. The purpose of this study was to examine the preemptive effect of systemic ketamine in rats undergoing a plantar incision. METHODS: Ketamine (10, 30, or 100 mg/kg) or a saline vehicle was administered subcutaneously 30 minutes before an incision was made. Withdrawal thresholds to calibrated von Frey filaments adjacent to the wound were measured before incision and from 2 hours to postoperative 6 days after incision. To evaluate the effectiveness of an extension of antinociceptive treatment into the initial postoperative period, 30 mg/kg ketamine or a saline vehicle 30 minutes before an incision was made was administered subcutaneously followed by injection of 5 more of the same drug or vehicle every 1 hour. The development of pain behavior was also evaluated before incision and from 30 minutes after last drug injection to postoperative 6 days. RESULTS: In saline vehicle-treated rats, mechanical hyperalgesia was persistent through day 1 after surgery and then gradually returned to the preincisional value. Thirty mg/kg ketamine increased the withdrawal threshold at 2 hours. One hundred mg/kg ketamine caused a motor block at 2 hours and increased the withdrawal threshold at 2.5 and 3 hours. A repeated injection of 30 mg/kg ketamine caused a motor block during the first 2 hours, and reduced hyperalgesia at 3 and 4 hours after the last drug injection. However, there were no significant differences in withdrawal thresholds among the groups at all subsequent times. CONCLUSIONS: Antinociceptive treatment of systemic ketamine covers the period of surgery and the initial postoperative period by reducing early pain behavior, but had no impact on subsequent measures of hyperalgesia. Therefore, a preemptive effect of systemic ketamine in postoperative pain seems unlikely.

Interaction between Bupivacaine, Ropivacaine and Diltiazem in the Isolated Rat Heart / 대한마취과학회지

BACKGROUND: Local anesthetics are often used for a regional block in patients who are being treated with calcium channel blockers (CCB). Bupivacaine is a local anesthetic with potential for serious cardiovascular toxicity. Ropivacaine is a relatively new local anesthetic. It is clinically equipotent and chemically similar to bupivacaine. Diltiazem (CCB) is a potent coronary and systemic vasodilator with antiarrhythmic properties. Local anesthetics such as bupivacaine and ropivacaine have been suggested to show drug interactions with diltiazem. Therefore, we tried to observe the drug interactions between bupivacaine, ropivacaine and diltiazem using an animal model. METHODS: This study was performed using an isolated rat heart (N = 40) by the Langendorff method. After a stabilization period, all hearts were subjected to the application of local anesthetics of a 1 microgram/ml or 3/ml concentration, respectively. Thereafter, they were subdivided into four groups; the bupivacaine (B) group, bupivacaine with diltiazem (BD) group, ropivacaine (R) group, and ropivacaine with diltiazem (RD) group. Parameters such as, LVP, dp/dt, heart rate (HR), coronary flow (CF), DO2, and MVO2 were measured. RESULTS: All parameters decreased in all groups, respectively (P < 0.05). The BD group and R group showed a lower LVP and dp/dt than those of the B group (P < 0.05). The BD group and B group showed lower HR than that of the R group (P < 0.05). The RD group showed a higher CF than other groups (P < 0.05). CONCLUSIONS: The negative inotropic potency of bupivacaine was enhanced in the presence of diltiazem. We suggest that diltiazem has a protective effect against reduction of CF by ropivacaine. Therefore, we should consider this when selecting local anesthetics for cardiovascular patients under the treatment of diltiazem.

The Effect of Preemptive Local Infiltration of Lidocaine and Gabapentin on Postoperative Pain in Rats / 대한마취과학회지

BACKGROUND: Preemptive analgesia may improve postoperative antinociceptive treatment that prevents the development of central sensitization which contributes to post-injury pain hypersensitivity. However, beneficial effects of preemptive analgesia appear controversial. The purpose of this study was to examine the effect of pre- and post-incisional local infiltration of lidocaine and gabapentin on incisional pain in rats. METHODS: Thirty five male rats were divided into 7 groups; control group (n = 5), pre-lidocaine infiltration group (n = 5), post-lidocaine infiltration group (n = 5), pre-gabapentin 10 mg infiltration group (n = 5), post-gabapentin 10 mg infiltration group (n = 5), pre-gabapentin 30 mg infiltration group (n = 5), and post-gabapentin 30 mg infiltration group (n = 5). To evaluate postoperative mechanical hyperalgesia in injured feet, withdrawal thresholds were measured by calibrated von Frey filaments at 2 hrs, 1, 2, 3, 4, and 5 days after an incision. RESULTS: The pre-lidocaine infiltration group shows better analgesic effects than post-lidocaine infiltration group until postoperative day 1 (P < 0.05). The gabapentin infiltration groups were effective in postoperative pain management but there were no significant differences between pre- and post- incisional treatment. CONCLUSIONS: A preemptive lidocaine injection has a good analgesic effect on incisional pain. Gabapentin also has a good analgesic effect on incisional pain.

Role of Nitric Oxide in Lipopolysaccharide-Induced Acute Lung Injury and Lipid Peroxidation in Rats / 대한마취과학회지

BACKGROUND: Nitric oxide (NO) may act as an oxygen radical scavenger or as an antioxidant, and inhibit neutrophil superoxide anion production. In contrast, NO combines with superoxide to form peroxynitrite, a very damaging material whose decomposition RESULTS in the generation of a hydroxyl radical. This study was designed to determine the role of NO in the development of acute lung injury and lipid peroxidation induced by lipopolysaccharide (LPS) in rats. METHODS: Male Sprague-Dawley rats (200 - 250 g) were given one of the following treatments; intraperitoneal normal saline 0.5 ml, intraperitoneal E. coli LPS (5 mg/kg) in 0.5 ml normal saline, 4 mg/kg L-N(6)-(1-iminoethyl)lysine (L-NIL) + LPS, or L-arginine (80 mg/kg) + LPS. Four hours after treatment, the rats were killed by an intraperitoneal pentobarbital injection (100 mg/kg) and plasma nitrate/nitrite concentration (Griess reagents) and lipid peroxide (LPO) concentration of the lung (Yagi's method) were measured (n = 8). In the other sets of experiments, myeloperoxidase activity of the lung (n = 5) and protein concentration of the bronchoalveolar lavage (BAL) fluid (BCA protein assay reagents, n = 4) were assayed. RESULTS: LPS treatment increased plasma nitrate/nitrite concentrations approximately 6 times (20.9 1.8nM, P < 0.01) compared with the control group (3.6 +/- 0.7nM), and L-NIL treatment prevented this increase. L-NIL plus LPS treatment resulted in greater increase of LPO concentrations of the lung compared with the control (P < 0.05). Myeloperoxidase activity and protein concentrations of BAL fluids were higher in LPS and L-NIL plus LPS treatment groups than the control group. CONCLUSIONS: These results suggest that inhibition of the increase of NO by selective inducible NO synthase inhibitor L-NIL may increase lipid peroxidation in septic rats.

Behavioral Effects of Different Concentrations of Formalin on Pain Test / 대한마취과학회지

BACKGROUND: The stimulus provided by a subcutaneous injection of formalin is tonic, moderate, continuous pain. We evaluated the effect of formalin at three concentrations, 1.5%, 2.5%, and 5% - 50nl to determine the relationship between formalin concentration and pain behaviors. METHODS: Male Sprague-Dawley rats (250 - 300 g body weight) were used. Following formalin (n = 8 each group) or saline (control group, n = 6) injection, flinching, licking, lifting, and favoring responses were recorded during the early (0 - 5 minutes after injection; phase 1) and late phases (20 - 60 minutes after injection, phase 2). Sham-injected rats (n = 4) underwent subcutaneous insertion of the needle, but no substance was injected. RESULTS: During both phases, flinching was more frequent in the 5% formalin group than in the control group (P < 0.05). As for the licking behavior, phase 1 of 2.5% and 5% formalin groups and phase 2 of all three groups showed longer durations than those in the control group, respectively (P < 0.05). As for the lifting behavior, phase 2 of the 2.5% and 5% group showed a longer duration than the control group (P < 0.05). There was no significant biphasic response of favoring in each group. CONCLUSIONS: Our findings indicate that the formalin concentration (2.5% or higher) plays an important role in inducing the biphasic response. Flinching and licking were the more spontaneous and robust biphasic parameters. In both phases, flinching was robust for 5% formalin.

The Effects of Diltiazem with Desflurane on Coronary Blood Flow and Contractility in Isolated Rat Heart / 대한마취과학회지

BACKGROUND: Calcium channel blockers and volatile anesthetics have depressant effects on cardiac function. Both groups of drugs appear to exert both qualitatively and quantitatively different effects on electrophys-iologic and mechanical function. The authors examined the direct in-vitro effects of diltiazem in the presence of a desflurane using an isolated rat heart. METHODS: Isolated Sprague-Dawley rat hearts (N = 40) were perfused at a constant pressure with an oxygenated modified Krebs' solution. After the stabilization period, they were subdivided into two groups. The groups were subjected to different concentrations of desflurane (6, 12, 18 vol%) alone or 100 ng/ml diltiazem with the same concentrations of desflurane, respectively. Isovolumetric left ventric ular pressure (LVP), heart rate and rate of change of ventricular pressure (dp/dt) were measured via a thin, saline-filled latex balloon and transducer. Coronary flow and oxygen tension were measured at the coronary inflow and outflow sites. Oxygen delivery, myocardial oxygen consumption and percent oxygen extraction were calculated with each measurement. RESULTS: The combination of diltiazem and desflurane (6, 12 and 18 vol%) dose-dependently depressed LVP and dp/dt more than desflurane alone. Coronary flow and oxygen delivery increased in a dose- dependent fashion, but there was no statistical difference between the groups. The decreases of heart rate, myocardial oxygen consumption and percentage of oxygen extraction were dependent on the concentration of desflurane. Arrhythmias occurred only with a high desflurane (18 vol%) concentration and the high desflurane concentration plus diltiazem. CONCLUSIONS: These results demonstrate that the myocardial depressant effect of diltiazem plus desflurane is greater than desflurane alone. The authors suggest that administration of diltiazem during high concentrations of desflurane anesthesia could result in deleterious cardiac depression and arrhythmias.

Protective Effect of Etomidate on Kainic Acid-induced Neurotoxicity in Rat Hippocampus / 대한마취과학회지

BACKGROUND: The present investigation was undertaken to evaluate the neuroprotective effect of etomidate against kainic acid (KA) induced neurotoxicity in rats by using the immunoreactivity of heat shock protein-70 (HSP-70) and the acid-fuchsin stain. METHODS: Administration of etomidate (20 mg/kg, I.P.) was performed in sequence; first being just one hour after a KA (10 mg/kg, I.P.) injection, then three more times at one hour intervals. Neuronal damages in the hippocampus were evaluated by using the acid-fuchsin stain to detect cell death and HSP-70 induction as an index of cell injury at 24 h after the administration of KA. RESULTS: HSP-70 induction and acid fuchsin positive neurons were increased in the CA1 and CA3 regions of the hippocampus after a KA injection but significantly decreased by an injection of etomidate (P < 0.01). CONCLUSIONS: These results suggest that the etomidate has a potential effect on the protection of neurons against KA-induced neurotoxicity.

Analgesic and Anti-inflammatory Effects of Ibuprofen, Indomethacin and NS-398 on an Acute Model of Arthritis in Rats / 대한마취과학회지

BACKGROUND: All currently available nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both cyclooxygenase-1 and cyclooxygenase-2 and exhibit many complications. It has been suggested that the anti-inflammatory and also most of the analgesic effects of NSAlDs result from an inhibition of arachidonic acid metabolites synthesised via cyclooxygenase-2. In the present study, the extent of analgesic and anti-inflammatory effects of ibuprofen (a non-selective cyclooxygenase inhibitor), indomethacin (a selective cyclooxygenase-1 inhibitor) and NS-398 (a selective cyclooxygenase-2 inhibitor) are investigated in on acute model of arthritis in rats by a behavior test and pathologic examination. METHODS: Arthritis was induced with 2% kaolin and 3% carrageenan into the right knee joint cavity under enflurane anesthesia (2 - 4%). Before and after the injection, rats were allowed to walk freely through a pathway, constructed to record weight load by means of 8 weight sensors attached to 8 plates which function independently. Weight bearing, the weight of rat and the diameter of the knee joint were measured serially before and after the injection. At 6 hours after the injection, ibuprofen, indomethacin and NS-398 were injected intraperitoneally (1, 5 and 25 mg/kg/ml). RESULTS: In the control group, weight bearing decreased maximally and the weight bearing ratio increased maximally at 6 hours after inflammation and the diameter ratio increased maximally 1 day after inflammation. There were improvements in weight bearing with ibuprofen, indomethacin and NS-398 in a dose-dependent manner at 8, 10 and 12 hours after induction of arthritis. NS-398 demonstrated better analgesic and anti-inflammatory effects than ibuprofen or indomethacin at a low dose (1 mg/kg). In contrast to NS-398, significant analgesic effects of indomethacin on the behavior test was not shown at a low dose. CONCLUSIONS: These results suggest that the selective cyclooxygenase-2 inhibitor plays an important role as an analgesic and anti-inflammatory drug.

Patterns of Nerve Conduction Blockade by Different Combinations of Lidocaine-bupivacaine Mixture / 대한마취과학회지

BACKGROUND: A mixture of local anesthetics such as lidocaine and bupivacaine has frequently been used in clinical practice. The rationale behind this is to take advantage of lidocaine's rapid onset and bupivacaine's perpetuation in anesthesia. The purpose of this study was to examine the changes in the onset and recovery of nerve blocking action exerted by the different combinations of these two in the mixture. METHODS: Isolated sciatic nerve preparations obtained from adult male Sprague-Dawley rats were used in this study. Recordings of A-fiber compound action potentials (A-CAPs) were made at the end of the isolated nerve while single pulse stimuli (0.5 msec, supramaximal intensity, 2 Hz) were applied to the opposite end of the nerve. Seven different composition of lidocaine-bupivacaine mixtures were prepared (0 : 6, 1 : 5, 2 : 4, 3 : 3, 4 : 2, 5 : 1, 6 : 0 vol./vol.), where basal concentrations of lidocaine and bupivacaine were 0.2% and 0.05%, respectively. Amplitudes of A-CAPs were measured before, during and after perfusion of mixture solution. The time needed for A-CAPs amplitude to decrease to 10% of the basal value after starting perfusion (onset time) and that needed to reach to 50% of the basal value after ceasing the perfusion (recovery time) were measured. RESULTS: With increasing concentration ratios of lidocaine to bupivacaine in the mixture as mentioned above, the following onset and recovery times were obtained (6.0 +/- 0.3, 5.6 +/- 0.3, 6.0 +/- 0.5, 8.3 +/- 0.5, 7.3 +/- 0.6, 7.8 +/- 0.3, and 10.8 +/- 0.8, minutes; 38 +/- 4, 63 +/- 12, 87 +/- 19, 100 +/- 13, 104 +/- 18, 137 +/- 27, and 157 +/- 18 minutes, respectively). CONCLUSION: Onset times were, in general, exponentially decreased with the increase in the lidocaine concentration. However, recovery times were lineary increased with the increase in the bupivacaine concentration. So, it should be kept in mind that rapid onset can only be obtained with the expense of substantial reduction in the duration of local anesthetic effect of the mixture, and vice versa.

Ultrastructural Changes of Nerve Fibers Using a Neuropathic Pain Model in a Rat / 대한마취과학회지

BACKGROUND: Neuropathic pain is part of the symptom complex known as peripheral neuropathy. Sensory loss, muscle weakness, atrophy, and decreased tendon reflexes are more common than pain in neuropathic disease. Recently, Bennett and Xie reported that when the sciatic nerve of a rat is loosely ligated, the rat develops pain syndrome similar to that observed in neuropathic pain states in a human. Anatomical and physiological studies to date indicate that the major pathological finding in large diameter myelinated fibers distal to the ligatures was a complex loss of response while in small myelinated fibers there were was only subtle changes. However, a more extensive analysis of the various nerve fiber groups in the damaged sciatic nerve is required for a better understanding of the pathophysiology of the present neuropathy. METHODS: To evaluate the damage and regeneration of all caliber of peripheral nerve, we performed an electron microscopic analysis of the sciatic nerve after four loose ligatures were applied. Cross- sectional photomicrographies of regions distal to the ligatures were studied. A peripheral mononeuropathy was produced in adult rats by tying 4 ligatures loosely around the common sciatic nerve. The distal part of the ligated common sciatic nerve was severed in 2 rats of each group at 1 day, 3 days, 1 week, 2 weeks and 4 weeks respectively. The severed nerves were prepared for electron microscopic examination and pathologic changes were observed under the electron microscope. RESULTS: The ultrastructural changes after ligature application were as follows: At 1 day, the axon of A-beta fiber was shrunken and detached from the myelin sheath. C-fibers were mildly edematous and A-delta fibers appeared to be normal. On the 3rd day, the axoplasm of A-beta fibers was more shrunken, containing swelling of microorganelles and irregularly thickened myelin sheath. C-fiber showed some degrees of degeneration. A-delta fibers revealed mild degeneration and interstitial edema was also noted. At 1 week, the myelin sheaths of A-beta fibers were severely irregular in appearance with marked axonal loss. Many myelin fragments were phagocytosed in the cytoplasm of adjacent Schwann cells. At 2 weeks, A-beta fibers predominantly disappeared and many fragmented myelin sheaths were ingested in the Schwann cell. In some areas, A-beta fibers partially regenerated, which involved remyelination and an increase in the numbers of microorganelles of the Schwann cells. C-fibers were also regenerated. At 4 weeks after sciatic nerve ligation, A-beta fibers regenerated and myelin ovoids were noted within the axoplasm of the A-beta fibers. Myelin ovoids were found in the Schwann cell cytoplasm. A-delta fibers and C-fibers appeared ultrastructurally well-regenerated and had a relatively normal distribution. CONCLUSIONS: We found that maximal nerve degeneration was observed at 2 weeks after sciatic nerve ligation, thereafter, nerve regeneration was noted at 4 weeks after sciatic nerve ligation.

The Effect of Adrenaline on the Blockade of Compound Action Potential by Local Anesthetics in Rat Sciatic Nerves / 대한마취과학회지

BACKGROUND: Adrenaline has often been used to prolong the local anesthetic effect during surgical procedures. As a possible explanation for this, a local vasoconstriction caused by adrenaline has been proposed. However, in a recent study, clonidine, an alpha2 adrenergic receptor agonist, was reported to block the conduction of mammalian nerves in vitro. Thus, there is a possibility that adrenaline may block nerve conduction by acting on the adrenergic receptor. The present study is performed to see : (1) If adrenaline directly affects nerve conduction ; (2) If adrenaline affects conduction blockade caused by local anesthetic. METHODS: Recordings of compound action potentials (CAPs) of A- and C-components were obtained from isolated sciatic nerves of adult male Sprague-Dawley rats. Dose-response curves of lidocaine and adrenaline regarding depression of CAPs were determined. Effects of adrenaline on the lidocaine-induced nerve block was assessed by comparing the effect of lidocaine (3.5x 10 5) with a lidocaine-epinephrine mixture (Lido-Epi, 3.5 x10 5 lidocaine with 1:100,000 epinephrine). RESULTS: Adrenaline, near the clinical concentrations, had no effect on the size of either A- or C-component of CAPs. The ED50 of lidocaine was 3.5x 10 5. Lidocaine depressed A-CAP 45.9+/- 7.0 when compared with baseline value, and the Lido-Epi solution depressed A-CAP to 41.7+/- 5.0 (P > 0.05). Lidocaine depressed C-CAP 59.8 +/- 3.4 when compared with the baseline value, and the Lido-Epi solution depressed C-CAP to 60.5 8.1 (P > 0.05). Consequently, adrenaline did not augment lidocaine induced nerve blockade. CONCLUSION: This study confirmed that adrenaline applied to the peripheral nerve has no effect either on nerve conduction itself or on conduction block produced by lidocaine.

Effects of Pretreated-Fentanyl on the Myocardial Function in Isolated Stunned Rat Heart / 대한마취과학회지

BACKGROUND: Fentanyl is commonly used as a anesthetics for patients who have poor cardiac reserve, because it provides cardiovascular stability. But little data exist on the effects of fentanyl on myocardial ischemia and reperfusion injury. The purpose of this study was to examine the effects of the fentanyl on the recovery of myocardial contracility, coronary flow, and myocardial oxygen balance in isolated rat hearts subjected to ischemia and reperfusion. METHODS: Isolated Sprague-Dawley rat hearts were perfused at constant pressure with oxygenated modified-Krebs solution (pH 7.4, 37oC). After stabilization period, all hearts were given fentanyl 0, 1, 10 ng/ml, respectively. Then, myocardial ischemia was induced by global ischemia for 15 minutes. Isovolumetric left ventricular pressure (LVP) and dP/dt were measured via a latex balloon and transducer. Also, coronary flow and oxygen tensions at the coronary inflow and outflow were measured. RESULTS: The application of fentanyl did not significantly affect myocardial contractility, coronary flow, and myocardial oxygen balance. After global ischemia, myocardial contractility, coronary flow, and myocardial O2 consumption were decreased, but percentage of O2 extraction was increased. However, these changes were not significantly different between fentanyl pretreated and control groups. CONCLUSIONS: These in vitro findings demonstrate that the pretreatment of fentanyl is devoid of major effects on recovery of the myocardial contracility, coronary flow, and myocardial oxygen balance in isolated stunned rat hearts.

The Effect of Ketamine on Norepinephrine Release in the Rat Hippocampus / 대한마취과학회지

BACKGREOUND: Since it has been reported that ketamine, an intravenous anesthetic, is a non-competitive antagonist of N-methyl-D-aspartic acid (NMDA) receptors, a large number of experimental data on the several mechanism of this process have been accumulated. But the mechanism about the effect of ketamine on neurotransmitter release in central nervous system has not been clearly elucidated yet. Therefore the present study was undertaken to investigate the effects of ketamine and thiopental sodium on hippocampal norepinephrine (NE) release, and also to examine the relationship between ketamine and NMDA receptor mechanisms in the rat hippocampus. METHODS: Slices from rat hippocampus were equilibrated with [3H]norepinephrine ([3H]NE) and the release of labelled products was evoked by electrical stimulation (3 Hz, 5 V/cm, 2 ms, rectangular pulses, 2 min), and the influence of various agents on the evoked tritium-outflow and the basal rate of release were investigated. RESULTS: In rat hippocampal slices, ketamine (1~30 micrometer) and thiopental sodium (1~30 micrometer) did not affect the evoked NE release and the basal release in the normal and Mg2 free medium. NMDA (3~100 micrometer) did not alter the NE release in the normal medium, but NMDA (1~30 micrometer) increased the basal rate of NE release in the Mg2 free medium. The increasing effects of NMDA on basal release were completely abolished by ketamine treatment in a concentration dependent manner. But, thiopental sodium did not affect the NMDA effect. CONCLUSIONS: These results suggest that increment of the basal rate of NE release is mediated by NMDA receptor in the rat hippocampus and ketamine completely block this effect, but thiopental sodium is not involved in these process.

The Effect of Nitric Oxide on Edema Formation in Cryogenic Brain Injury Model of the Rat / 대한마취과학회지

BACKGROUND: Nitric oxide (NO) is a simple molecule with a complex involvement in a wide variety of biologic functions. However, whether NO protects or aggravates brain injury is still controversial. This study was conducted to determine the effect of nitric oxide on the formation of brain edema resulting from a focal cryogenic injury in rats. METHODS: Thirty nine Sprague-Dawley rats (200~250 gm) were allowed food and water ad libitum. Anesthesia was induced in a specially designed plastic box with 5% halothane in oxygen. In experiment I (24 rats), animals were divided randomly into eight group (3 rats in each group) according to the decapitation time in control, 15, 30, 45, 60, 90, 120, and 180 min. Cryogenic injury was made by pouring liquid nitrogen to exposed temporo-parietal area through metal funnel for 60 seconds. After cryogenic injury, brain was quickly removed and cerebral hemispheres were seperated. Separated cerebral hemispheres were dried in a drying oven for 7 days at 60 degrees C. Cerebral water content was assessed by dry-weight method. In experiment II (15 rats), one subgroup (n=8) was control group, normal saline 0.5 ml was injected intraperitoneally 30 minutes before injury. the other (n=7) was experimental group, and a competitive nitiric oxide synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), was given intraperitoneally 30 minutes before injury in a dose of 20 mg/kg. Body temperature was monitored during whole experiment. Ninety minutes after injury, brain was quickly removed and cerebral hemispheres were seperated. The cerebral water content of separated cerebral hemisphere was assessed by dry-weight method. RESULTS: In time courses of cryogenic brain edema of experiment I, the amount of brain edema was increased till 90 minutes after cryogenic brain injury and then decreased. In L-NAME group of ex-periment II, the amount of cerebral edema was not changed significantly (p<0.05). But, there was a tendency of decrease in brain edema formation in L-NAME group than control group. CONCLUSION: It was not proved that nitric oxide had a major role in the edema formation aftercryogenic brain injury, but it still seems that nitric oxide has at least partly involved in the pathogenesis of cerebral edema resulting from traumatic brain injury.

Effects of Enflurane on the Left Ventricular Function in Isolated Diltiazem-Pretreated Rat Heart / 대한마취과학회지

BACKGROUND: Calcium channel blockers and volatile anesthetics have depressant effects on cardiac function. Both of them appear to exert, qualitatively and quantitatively, different effects on myocardial contractility, coronary flow, and myocardial oxygen balance. The aim of this study was to examine the direct cardiac effects of the enflurane in the presence of diltiazem. METHODS: Isolated Sprague-Dawley rat hearts (N=45) were perfused at constant pressure with oxygenated Modified-Krebs solution (pH 7.4, 37oC). Isovolumetric left ventricular pressure (LVP) and dP/dt were measured via a latex balloon and transducer. Also, coronary flow and oxygen tensions at the coronary inflow and outflow were measured. After stabilization period, all hearts were subjected to the application with diltiazem (100 ng/ml). Thereafter, they were subdivided into three groups; group 1, 2, 3. Groups subjected to the combination of diltiazem (100 ng/ml) with enflurane 1.1, 2.2, or 3.3 vol%, respectively. RESULTS: After the application of diltiazem, myocardial contractility and heart rate were significantly decreased, and coronary flow were significantly increased. The combination of diltiazem with enflurane depressed myocardial contractility, heart rate, myocardial O2 consumption, and percentage of O2 extraction more than diltiazem alone, and their effects were dependent on the concentration of enflurane. However, there was no difference in the change of coronary flow and oxygen delivery between diltiazem and the combination of diltiazem with enflurane. CONCLUSIONS: These in vitro findings demonstrate that the combination of diltiazem with enflurane shows greater direct negative inotropic and negative chronotropic effect, and is associated with less attenuation of coronary autoregulation, but with a larger reduction in O2 utilization. The present results suggest that high enflurane anesthesia in the diltiazem-pretreated patients could result in profound cardiac depression.