Assessing effects of tamoxifen on tolerance, dependence, and glutamate and glutamine levels in frontal cortex and hippocampus in chronic morphine treatment.

Tamoxifen has been shown to reduce glutamate release from presynaptic glutamatergic nerves and reverse tolerance to morphine-induced respiratory depression. Changes in glutamatergic neurotransmission in the central nervous system contribute to morphine tolerance, dependence, and withdrawal. This study, therefore, evaluated effects of tamoxifen on development of analgesic tolerance and dependence, and brain glutamate and glutamine levels in chronic morphine administration. Mice implanted with placebo or morphine pellets were injected with tamoxifen (0.6-2 mg/kg) or vehicle twice daily for 3 days. Nociceptive response was evaluated in the hot plate and tail immersion tests, 4, 48 and 72 h post-implant, and following a challenge dose of morphine (10 mg/kg). Withdrawal signs were determined after naloxone (1 mg/kg) administration. Morphine increased nociceptive threshold which declined over time. At 72 h, acute morphine elicited tolerance to the analgesic effect in the hot plate test in vehicle or tamoxifen administered animals. In the tail immersion test, however, tolerance to morphine analgesia was observed in tamoxifen, but not vehicle, co-administration. Tamoxifen did not reduce withdrawal signs. In contrast to previous reports, glutamate and glutamine levels in the hippocampus and frontal cortex did not change in the morphine-vehicle group. Confirming previous findings, tamoxifen (2 mg/kg) decreased glutamate and glutamine concentrations in the hippocampus in animals with placebo pellets. Both doses of tamoxifen significantly changed glutamate and/or glutamine concentrations in both regions in morphine pellet implanted animals. These results suggest that tamoxifen has no effect on dependence but may facilitate tolerance development to the antinociception, possibly mediated at the spinal level, in chronic morphine administration.

Effect of oxytocin pretreatment on the development of morphine tolerance and dependence in rats.

Increased opioid synthesis and release, and enhanced alpha-2 adrenoceptor signaling have been suggested to mediate repeated oxytocin-induced long-lasting effects including elevated pain threshold in rats. This study evaluated whether oxytocin pretreatment would influence development of dependence and tolerance to the nociceptive and body temperature responses to morphine and enhance effects of alpha-2 adrenergic agonist clonidine on nociceptive threshold, body temperature and morphine withdrawal signs. Rats injected subcutaneously with saline or 1 mg/kg oxytocin for 5 days were implanted with placebo or morphine pellets 24 h after the treatment period. Body temperature and nociception were assessed, with nociception determined via by hot plate and tail immersion tests, before and 4, 24 and 48 h after pellet implantation, and following a challenge dose of morphine. Withdrawal signs were determined after naloxone administration. Oxytocin produced analgesia, as evidenced by increased paw withdrawal latency in the hot plate test. Morphine increased body temperature and nociceptive threshold which declined over time. Morphine challenge could not demonstrate tolerance to the body temperature response. Analgesic tolerance was observed in the hot plate test in saline and in both tests in oxytocin pretreated rats. Naloxone-precipitated withdrawal appeared to be less severe in oxytocin pretreatment. Clonidine was ineffective on the withdrawal signs but decreased body temperature and increased tail flick latency in the tail immersion test in oxytocin pretreated animals. These results, while producing evidence for a hyperresponsiveness in alpha-2 adrenoceptors, provide contrasting effects on morphine tolerance and dependence, and their partial mediation by opioidergic and adrenergic activation in repeated oxytocin treatment.

Effects of scopolamine treatment and consequent convulsion development in c­fos expression in fed, fasted, and refed mice.

Fasting, anticholinergics, and seizures affect c­fos activation in the brain. Additionally, antimuscarinic treated fasted animals develop convulsion soon after re­feeding. Therefore, we assessed whether c­fos expression changes in fed, fasting, and refed animals and how scopolamine treatment affects these changes. We further assessed whether there is a change in c­fos expression after convulsions. For this purpose, BALB/c mice fasted for 1, 3, 6, 12, 24 and 48 h periods were used. The animals were treated with saline or scopolamine. Half\r\nof the animals treated with saline or scopolamine were given food 20 min after injection. All animals were observed for development of convulsions for 30 min. At the end of this period, the brains of all animals were removed, and the percentage of c­fos active cells in the hypothalamus was determined immunohistochemically. Convulsions occurred within 1­48 h of fasting, after scopolamine treatment and re­feeding. Compared to fed animals, c­fos expression was not significantly changed in those undergoing different fasting periods, but significantly decreased after 12 h fasting. After animals were allowed to eat, c­fos activation significantly increased in the 1, 3, 6 and 12 refed­saline groups and decreased in the 48 refed­saline group. Scopolamine treatment in 1­24 h fasted animals increased c­fos expression, but decreased in 48 h fasted animals. Whereas convulsion development in scopolamine­treated 3, 6, 12 and 24 h refed animals suppressed c­fos expression. These results demonstrate that re­feeding and scopolamine treatment induces neuronal activity in the hypothalamus, while scopolamine induced convulsions after food intake suppressed the c­fos activity.

Effects of tamoxifen and glutamate and glutamine levels in brain regions in repeated sleep deprivation-induced mania model in mice.

Protein kinase C inhibitor tamoxifen reduces symptoms of acute mania in bipolar patients and mania-like behaviors in animals. Memory impairment and altered levels of glutamate and glutamate/glutamine ratio have been reported in mania. Tamoxifen suppresses glutamate release which plays an important role in memory. The present study evaluated whether tamoxifen's activity participates in its antimanic efficacy in repeated sleep deprivation mania model. Mice were divided into control and 24-h sleep-deprived groups and were treated with vehicle or 1 mg/kg tamoxifen twice daily for 8 days. Sleep deprivation was repeated three times at intervals of 2 days. Square crossing and rearing were recorded as measures of locomotor activity. Memory and risk taking behavior were evaluated using novel object recognition and staircase tests, respectively. Glutamate and glutamine levels were measured in the frontal cortex and hippocampus. Behavioral tests were conducted 24 h after the second or immediately after the third sleep deprivations. Sleep deprivation increased locomotor activity and risk taking. Glutamate and glutamine levels and glutamate/glutamine ratio in the frontal cortex and hippocampus were unaffected. Locomotor hyperactivity was prevented by tamoxifen treatment. No change in the recognition index suggested lack of memory impairment in the model. These findings confirm the relevance of repeated sleep deprivation as a mania model and tamoxifen as an antimanic agent. However, future research is needed to further address lack of memory impairment in the model and lack of glutamatergic influence on the model and antimanic effect of tamoxifen.

Ketamine and its combinations with valproate and carbamazepine are ineffective against convulsions induced by atropine treatment and food intake in fasted mice.

OBJECTIVES: Fasted rodents treated with antimuscarinics develop convulsions after refeeding. Food deprivation for 48 hr produces changes in [3H]glutamate binding suggesting glutamatergic contribution to the underlying mechanism of the seizures that are somewhat unresponsive to antiepileptics. Studies in animals and epileptic patients yielded considerable information regarding the anticonvulsant effect of the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine. Thus, this study evaluated the efficacy of ketamine and its combinations with valproate and carbamazepine on convulsions in fasted animals. MATERIALS AND METHODS: Following 24 hr of fasting, mice were given saline, 5 or 10 mg/kg ketamine, 250 mg/kg sodium valproate, 24 mg/kg carbamazepine, 5 mg/kg ketamine+sodium valproate, or 5 mg/kg ketamine+carbamazepine and then were treated with saline or 2.4 mg/kg atropine (5-9 mice per group). The animals were observed for the occurrence of convulsions after being allowed to eat ad libitum. RESULTS: Ketamine, valproate and carbamazepine pretreatments were ineffective in preventing the convulsions developed after atropine treatment and food intake in fasted animals. The incidence of convulsions was significantly higher in 5 and 10 mg/kg ketamine, carbamazepine, and carbamazepine+ketamine groups, but not in the valproate and valproate+ketamine treated animals. CONCLUSION: In contrast to previous findings obtained with the NMDA antagonist dizocilpine (MK-801), ketamine lacks activity against convulsions developed after fasting. The drug does not enhance the efficacy of valproate and carbamazepine either. Using different doses of ketamine or other NMDA antagonists, further studies may better clarify the anticonvulsant effect of ketamine and/or role of glutamate in these seizures.

Contribution of M1 and M2 muscarinic receptor subtypes to convulsions in fasted mice treated with scopolamine and given food.

Treatment of fasted mice and rats with the nonselective muscarinic antagonist, scopolamine or atropine, causes convulsions after food intake. This study evaluated the effect of fasting on the expression of M1 and M2 muscarinic receptors in the brain regions, the relationship between receptor expression and seizure stages, and the muscarinic receptor subtype which plays a role in the occurrence of convulsions. Mice were grouped as allowed to eat ad lib (fed) and deprived of food for 24h (fasted). Fasted animals developed convulsions after being treated with scopolamine (60%) or the selective M1 receptor antagonist pirenzepine (10mg/kg; 20% and 60mg/kg; 70%) and given food. Fasting increased expression of M1 receptors in the frontal cortex and M2 receptors in the hippocampus, but produced no change in the expression of both receptors in the amygdaloid complex. Food intake after fasting decreased M1 receptor expression in the frontal cortex and M1 and M2 receptor expression in the hippocampus. Seizure severity was uncorrelated with muscarinic receptor expression in the brain regions. Taken together, these findings provide evidence for the role of M1 muscarinic receptor antagonism and fasting-induced increases in M1 and M2 expression possible underlying mechanism in the occurrence of convulsions in fasted animals.

Impact of Topiramate on Rat Phrenic Nerve-Hemidiaphragm Preparations.

INTRODUCTION: Topiramate has a negative modulatory effect on voltage-gated ion channels involved in neuromuscular junction transmission. To investigate the potential impact of topiramate on muscle contraction, phrenic nerve-hemidiaphragm preparations were used as a neuromuscular junction model. METHODS: Phrenic nerve-hemidiaphragm preparations were isolated from rats and were mounted in oxygenated Krebs solution. Preparations were stimulated in the presence of topiramate and phenytoin with a rectangular pulse at 0.1 Hertz, 0.3 miliseconds, and 3 miliseconds of duration, forming indirect, direct single, and tetanic muscle contractions, respectively. The expressed tension was isometrically recorded via a force displacement transducer on a polygraph. RESULTS: Topiramate and phenytoin directly and indirectly reduced contractions in a time-dependent manner. By contrast, topiramate, but not phenytoin, showed an excitatory effect on contraction in tetanic potentiation. CONCLUSION: To our knowledge, our study is the first to show the effects of topiramate on muscle contraction and neuromuscular junction transmission. Topiramate needs to be used with caution in patients with muscle weakness and respiratory problems.

Effects of Cilostazol and Diltiazem Hydrochloride on Ischemia-Reperfusion Injury in a Rat Hindlimb Model.

OBJECTIVE: Free radicals and neutrophils are potent sources of ischemia-reperfusion injury (I/R) and they can be limited by the use of exogenous application of some therapeutic agents. The objective of this study was to compare the effects of cilostazol and diltiazem hydrochloride in a rat hind limb model of I/R injury. Methods: Skeletal muscles submitted to 2 hours of ischemia by placing an aneurysm clip to femoral artery and reperfused after 1, 2 and 4 hours. Seventy-two Wistar-Albino rats were randomly divided into mainly four groups according to treatment agents:  Group I (control group) was treated with saline; Group II was treated with diltiazem hydrochloride; Group III was treated with cilostazol in 30% dimethyl sulphoxide; and Group IV was treated with 30% dimethyl sulphoxide intraperitoneally. These four main groups also subdivided into three subgroups according to duration of the reperfusion times.  Blood samples were taken and all rats were sacrificed. Results: Cilostazol-treated groups demonstrated a significant decrease in tissue and serum malondialdehyde (MDA) levels, and tissue myeloperoxidase (MPO ) activity compared with other groups. Increase in serum nitric oxide (NOx) level was significantly higher in all subgroups of cilastazol, diltiazem hydrochloride, and dimethyl sulphoxide groups versus the control group. CONCLUSION: Although these results suggest the beneficial effects of cilostazol and diltiazem hydrochloride on I/R injury, the effect of cilostazol on I/R injury seems to be more efficient than diltiazem hydrochloride.

Antimuscarinic-induced convulsions in fasted mice after food intake: No evidence of spontaneous seizures, behavioral changes or neuronal damage.

Prolonged or repeated seizures have been shown to cause spontaneous recurrent seizures, increased anxiety­related behavior, locomotor hyperactivity, impaired functions of learning and memory, and neuronal damage in the hippocampus and other brain regions in animals. Mice and rats treated with antimuscarinic drugs after fasting for two days or less develop convulsions after being allowed to eat ad libitum. To address whether such behavioral and neuroanatomic changes occur following these convulsions, mice treated i.p. with saline (control) or 2.4 mg/kg atropine and given food after 24 h of fasting were grouped according to seizure scores for behavioral and histological analysis. Following convulsions, the occurrence of spontaneous recurrent seizures was observed for 30 days. Motor activity and grooming behavior were assessed in the open field, and memory was assessed using the novel object recognition test 4 and 7 days after onset of convulsions, respectively. Animals allocated for the histological analysis were decapitated 7 days after onset of convulsions and hippocampal slices were evaluated for the percentage of degenerating neurons stained with Fluoro­Jade C. Spontaneous recurrent seizures, locomotor alterations, anxiety­related behavior, memory impairment, and neuronal loss in the granular layer of the dentate gyrus were not detected in the animals with seizure score 1-2 or 3-5. These results are in accordance with those related to the absence of behavioral changes, cognitive deficits, and hippocampal neuronal damage after single brief seizures in animals and patients with epilepsy.

Learning and memory in the forced swimming test: effects of antidepressants having varying degrees of anticholinergic activity.

The antidepressant-induced reduction in immobility time in the forced swimming test may depend on memory impairment due to the drug's anticholinergic efficacy. Therefore, the present study evaluated learning and memory of the immobility response in rats after the pretest and test administrations of antidepressants having potent, comparatively lower, and no anticholinergic activities. Immobility was measured in the test session performed 24 h after the pretest session. Scopolamine and MK-801, which are agents that have memory impairing effects, were used as reference drugs for a better evaluation of the memory processes in the test. The pretest administrations of imipramine (15 and 30 mg/kg), amitriptyline (7.5 and 15 mg/kg), trazodone (10 mg/kg), fluoxetine (10 and 20 mg/kg), and moclobemide (10 and 20 mg/kg) were ineffective, whereas the pretest administrations of scopolamine (0.5 mg/kg) and MK-801 (0.1 mg/kg) decreased immobility time suggesting impaired "learning to be immobile" in the animals. The test administrations of imipramine (30 mg/kg), amitriptyline (15 mg/kg), moclobemide (10 mg/kg), scopolamine (0.5 and 1 mg/kg), and MK-801 (0.1 mg/kg) decreased immobility time, which suggested that the drugs exerted antidepressant activity or the animals did not recall that attempting to escape was futile. The test administrations of trazodone (10 mg/kg) and fluoxetine (10 and 20 mg/kg) produced no effect on immobility time. Even though the false-negative and positive responses made it somewhat difficult to interpret the findings, this study demonstrated that when given before the pretest antidepressants with or without anticholinergic activity seemed to be devoid of impairing the learning process in the test.

Scopolamine-induced convulsions in fasted animals after food intake: sensitivity of C57BL/6J mice and Sprague-Dawley rats.

Food intake triggers convulsions in fasted BALB/c mice and Wistar albino rats treated with antimuscarinic drugs, scopolamine or atropine. Inbred strain studies have yielded considerable information regarding genetic influences on seizure susceptibility and factors contribute to epileptogenesis in rodents. This study, therefore, investigated sensitivity to antimuscarinic-induced seizures in C57BL/6J mice and Sprague-Dawley rats. Food deprivation for 48h in mice and 52h in rats did not produce strain differences in body weight loss. Fasted animals treated i.p. with 3mg/kg scopolamine developed convulsions after food intake. The incidence of convulsions was indifferent in comparison to BALB/c mice and Wistar albino rats. Number of animals developing stage 5 was more and onset of convulsions was longer in C57BL/6J mice than in BALB/c mice. Strain-related differences in sensitivity to seizures in C57BL/6J mice may need further evaluation for investigating genetic influences on scopolamine-induced seizures.

Neurotoxic effects of levobupivacaine and fentanyl on rat spinal cord / Efeitos neurotóxicos de levobupivacaína e fentanil sobre a medula espinhal de ratos / Efectos neurotóxicos de la levobupivacaína y el fentanilo sobre la médula espinal de ratones

BACKGROUND: The purpose of the study was to compare the neurotoxic effects of intrathecally administered levobupivacaine, fentanyl and their mixture on rat spinal cord. METHODS: In experiment, there were four groups with medication and a control group. Rats were injected 15 µL saline or fentanyl 0.0005 µg/15 µL, levobupivacaine 0.25%/15 µL and fentanyl 0.0005 µg + levobupivacaine 0.25%/15 µL intrathecally for four days. Hot plate test was performed to assess neurologic function after each injection at 5th, 30th and 60th min. Five days after last lumbal injection, spinal cord sections between the T5 and T6 vertebral levels were obtained for histologic analysis. A score based on subjective assessment of number of eosinophilic neurons - Red neuron - which means irreversible neuronal degeneration. They reflect the approximate number of degenerating neurons present in the affected neuroanatomic areas as follows: 1, none; 2, 1-20%; 3, 21-40%; 4, 41-60%; and 5, 61-100% dead neurons. An overall neuropathologic score was calculated for each rat by summating the pathologic scores for all spinal cord areas examined. RESULTS: In the results of HPT, comparing the control group, analgesic latency statistically prolonged for all four groups.In neuropathologic investment, the fentanyl and fentanyl + levobupivacaine groups have statistically significant high degenerative neuron counts than control and saline groups. CONCLUSIONS: These results suggest that, when administered intrathecally in rats, fentanyl and levobupivacaine behave similar for analgesic action, but fentanyl may be neurotoxic for spinal cord. There was no significant degeneration with levobupivacaine, but fentanyl group has had significant degeneration. .

JUSTIFICATIVA: O objetivo deste estudo foi comparar os efeitos neurotóxicos da administração por via intratecal de levobupivacaína e fentanil e suas misturas sobre a medula espinhal de ratos. MÉTODOS: O experimento compreendeu quatro grupos que receberam medicamento e um grupo controle. Os ratos foram submetidos a injeção de salina (15 µL) ou fentanil (0,0005 µg/15 mL), levobupivacaína a 0,25% (15 µL) e fentanil (0,0005 µg + levobupivacaína a 0,25%/15 µL) por via intratecal durante quatro dias. O teste de placa quente foi usado para avaliar a função neurológica após cada injeção nos minutos cinco, 30 e 60. Cinco dias após a última injeção lombar, secções da medula espinhal entre os níveis vertebrais T5 e T6 foram obtidas para análise histológica. Usamos um escore com base na avaliação subjetiva do número de neurônios eosinofílicos (neurônios vermelhos), o que significa degeneração neuronal irreversível. Esses neurônios refletem o número aproximado de neurônios em degeneração presentes nas áreas neuroanatômicas afetadas da seguinte forma: 1 = nenhum; 2 = 1-20%; 3 = 21-40%; 4 = 41-60% e 5 = 61-100% neurônios mortos. Um escore neuropatológico global foi calculado para cada rato pela soma dos escores patológicos para todas as áreas examinadas da medula espinhal. RESULTADOS: Nos resultados do TPQ, comparando o grupo controle, a latência analgésica foi estatisticamente prolongada para todos os quatro grupos.Em investimento neuropatológico, os grupos fentanil e fentanil + levobupivacaína apresentaram degeneração neuronal em contagens significativamente mais altas di que os grupos controle e salina. CONCLUSÕES: Esses resultados sugerem que fentanil e levobupivacaína, quando administrados por via intratecal em ratos, se comportam de forma semelhante à ação analgésica, mas fentanil pode ser neurotóxico para a medula espinhal. Não houve degeneração significativa com levobupivacaína, mas o grupo fentanil apresentou degeneração significativa. .

JUSTIFICACIÓN: El objetivo de este estudio fue comparar los efectos neurotóxicos de la administración por vía intratecal de la levobupivacaína y el fentanilo y su mezcla sobre la médula espinal de ratones. MÉTODOS: El experimento abarcó 4 grupos que recibieron medicamento y un grupo control. Los ratones recibieron inyección de solución salina (15 µL) o fentanilo (0,0005 µg/15µL), levobupivacaína al 0,25% (15 µL) y fentanilo (0,0005 µg + levobupivacaína al 0,25%/15 µL) por vía intratecal durante 4 días. Se empleó el test de placa caliente para evaluar la función neurológica tras cada inyección en los minutos 5, 30 y 60. Cinco días después de la última inyección lumbar, se obtuvieron las secciones de la médula espinal entre los niveles vertebrales T5 y T6 para el análisis histológico. Usamos una puntuación basándonos en la evaluación subjetiva del número de neuronas eosinofílicas (neuronas rojas), lo que significa degeneración neuronal irreversible. Esas neuronas reflejan el número aproximado de neuronas en degeneración presentes en las áreas neuroanatómicas afectadas de la siguiente forma: 1 = ninguna; 2 = 1-20%; 3 = 21-40%; 4 = 41-60% y 5 = 61-100% neuronas muertas. Para cada ratón se calculó una puntuación neuropatológica global a través de la suma de las puntuaciones patológicas de todas las áreas examinadas de la médula espinal. RESULTADOS: En los resultados del test de placa caliente, comparando el grupo control, la latencia analgésica fue estadísticamente prolongada para los 4 grupos.En la inversión neuropatológica, los grupos fentanilo y fentanilo + levobupivacaína tuvieron una degeneración neuronal en recuentos significativamente más altos que los grupos control y salina. CONCLUSIONES: Esos resultados nos sugieren que el fentanilo y la levobupivacaína, cuando se administran por vía intratecal en ratones, se comportan de forma similar a la acción analgésica, pero el fentanilo puede ser neurotóxico para la médula espinal. No hubo ...

Spontaneous withdrawal in intermittent morphine administration in rats and mice: effect of clonidine coadministration and sex-related differences.

BACKGROUND/AIM: Treating animals repeatedly with intermittent and increasing morphine doses has been suggested to allow some withdrawal during each dosing interval, which causes repeated stress. The present study aimed to test this hypothesis and assess sex-related differences in withdrawal signs and their suppression by clonidine. MATERIALS AND METHODS: Male and female rats and mice were administered with increasing doses of morphine twice daily at different dosing intervals. Rats were given clonidine in drinking water (5 µg/mL). Spontaneous and naloxone-precipitated withdrawal signs and novelty-induced grooming were evaluated. RESULTS: Male rats and male and female rats displayed manifestations of morphine withdrawal at the end of 14-h and 24-h dosing intervals, respectively. Clonidine attenuated the severity of the withdrawal signs. Male but not female mice displayed withdrawal signs at the end of 12-h and 17-h dosing intervals. Female mice exhibited less pronounced naloxone-precipitated withdrawal syndrome. Grooming did not reflect a "stress-like state" in morphine-treated animals. CONCLUSION: These findings indicate intermittent morphine treatment-induced spontaneous withdrawal in rats and mice and sex-related differences in spontaneous and naloxone-precipitated withdrawal signs in mice. Since the treatment protocol closely parallels the drug use pattern in opioid addicts, further experiments are needed to clarify the stress associated with the treatment and the efficacy of sedatives.

[Neurotoxic effects of levobupivacaine and fentanyl on rat spinal cord]. / Efeitos neurotóxicos de levobupivacaína e fentanil sobre a medula espinhal de ratos.

BACKGROUND: The purpose of the study was to compare the neurotoxic effects of intrathecally administered levobupivacaine, fentanyl and their mixture on rat spinal cord. METHODS: In experiment, there were four groups with medication and a control group. Rats were injected 15µL saline or fentanyl 0.0005µg/15µL, levobupivacaine 0.25%/15µL and fentanyl 0.0005µg+levobupivacaine 0.25%/15µL intrathecally for four days. Hot plate test was performed to assess neurologic function after each injection at 5th, 30th and 60th min. Five days after last lumbal injection, spinal cord sections between the T5 and T6 vertebral levels were obtained for histologic analysis. A score based on subjective assessment of number of eosinophilic neurons - Red neuron - which means irreversible neuronal degeneration. They reflect the approximate number of degenerating neurons present in the affected neuroanatomic areas as follows: 1, none; 2, 1-20%; 3, 21-40%; 4, 41-60%; and 5, 61-100% dead neurons. An overall neuropathologic score was calculated for each rat by summating the pathologic scores for all spinal cord areas examined. RESULTS: In the results of HPT, comparing the control group, analgesic latency statistically prolonged for all four groups. In neuropathologic investment, the fentanyl and fentanyl+levobupivacaine groups have statistically significant high degenerative neuron counts than control and saline groups. CONCLUSIONS: These results suggest that, when administered intrathecally in rats, fentanyl and levobupivacaine behave similar for analgesic action, but fentanyl may be neurotoxic for spinal cord. There was no significant degeneration with levobupivacaine, but fentanyl group has had significant degeneration.

Assessment of rewarding and reinforcing properties of biperiden in conditioned place preference in rats.

Biperiden is one of the most commonly abused anticholinergic drugs. This study assessed its motivational effects in the acquisition of conditioned place preference in rats. Biperiden neither produced place conditioning itself nor enhanced the rewarding effect of morphine. Furthermore, biperiden in combination with haloperidol also did not affect place preference. These findings suggest that biperiden seems devoid of abuse potential properties at least at the doses used.

Effects of insulin-like growth factor-I and platelet-rich plasma on sciatic nerve crush injury in a rat model.

OBJECT: Local administration of insulin-like growth factor-I (IGF-I) has been shown to increase the rate of axon regeneration in crush-injured and freeze-injured rat sciatic nerves. Local administration of platelet-rich plasma (PRP) has been also shown to have a measurable effect on facial nerve regeneration after transection in a rat model. The objective of the study was to compare the effects of locally administered IGF-I and PRP on the parameters of the Sciatic Function Index (SFI), sensory function (SF), axon count, and myelin thickness/axon diameter ratio (G-ratio) in a rat model of crush-injured sciatic nerves. METHODS: The right sciatic nerve of Wistar albino rats (24 animals) was crushed using a Yasargil-Phynox aneurysm clip for 45 minutes. All animals were randomly divided into 3 groups: Group 1 (control group) was treated with saline, Group 2 was treated with IGF-I, and Group 3 was treated with PRP. Injections were performed using the tissue expander's injection port with a connecting tube directed at the crush-injured site. Functional recovery was assessed with improvement in the SFI. Recovery of sensory function was using the pinch test. Histopathological examination was performed 3 months after the injury. RESULTS: The SFI showed an improved functional recovery in the IGF-I-treated animals (Group 2) compared with the saline-treated animals (Group 1) 30 days after the injury. In IGF-I-treated rats, sensory function returned to the baseline level significantly faster than in saline-treated and PRP-treated rats as shown in values between SF-2 and SF-7. The G-ratios were found to be significantly higher in both experimental groups than in the control group. CONCLUSIONS: This study suggests that the application of IGF-I to the crush-injured site may expedite the functional recovery of paralyzed muscle by increasing the rate of axon regeneration.

Ischemia/reperfusion in rat: antioxidative effects of enoant on EEG, oxidative stress and inflammation.

PRIMARY OBJECTIVE: The present study was undertaken to evaluate whether enoant, which is rich in polyphenols, has any effect on electroencephalogram (EEG), oxidative stress and inflammation in ischemia/reperfusion (I/R) injury. METHODS: Ischemia was induced by 2-hour occlusion of bilateral common carotid artery. Animals orally received enoant. Group 1 was the ischemic control group. Group 2 was treated with enoant of 1.25 g kg⁻¹ per day for 15 days after I/R. Group 3 received the same concentration of enoant as in group 2 for 15 days before and after I/R. Group 4 was the sham operation group. EEG activities were recorded and the levels of TNF-α, IL-1ß and IL-6, TBARS and GSH were measured in the whole brain homogenate. RESULTS: There were significant changes in EEG activity in groups treated with enoant either before or after ischemia when compared with their basal EEG values. TNF-α, IL-6 and IL-1ß levels were significantly increased after I/R. GSH levels in group 3 treated with enoant in both pre- and post-ischemic periods were significantly increased and TBARS concentration was decreased compared with the ischemic group. CONCLUSION: The findings support that both pre-ischemic and post-ischemic administrations of enoant might produce neuroprotective action against cerebral ischemia.

Seizures triggered by food intake in antimuscarinic-treated fasted animals: evaluation of the experimental findings in terms of similarities to eating-triggered epilepsy.

Food intake triggers convulsions in fasted mice and rats treated with antimuscarinic drugs, scopolamine or atropine. Bearing some similarities in triggering factor and manifestations of the seizures in patients with eating-evoked epilepsy, seizures in fasted animals may provide insight into the mechanism(s) of this rare and partially controlled form of reflex epilepsy.

Scopolamine-induced convulsions in fasted mice after food intake: evaluation of the sedative effect in the suppression of convulsions.

Food intake triggers convulsions in fasted mice and rats treated with antimuscarinic drugs, scopolamine or atropine. Most of the drugs produced anticonvulsant efficacy in these convulsions have sedative effects. Thus, the present study was performed to evaluate the contribution of sedation in the suppression of convulsions by using sedative drugs chlorpromazine, morphine, amitriptyline and diphenhydramine. Mice fasted for 24h and treated with 3mg/kg scopolamine developed convulsions soon after refeeding. Treatment of chlorpromazine and morphine during food deprivation did not provide a preventive effect in the development of convulsions observed after food intake in fasted animals. Pretreatment of amitriptyline, but not diphenhydramine, before scopolamine treatment suppressed the incidence of convulsions. Present results could not clearly demonstrate the role played by sedative effect in suppression of convulsions in fasted animals.

The role of solid food intake in antimuscarinic-induced convulsions in fasted mice.

Animals treated with scopolamine after fasting develop convulsions after they are allowed to eat ad libitum. This study was aimed at investigating the effect on these convulsions of liquid food intake, feeding by gavage, and placebo. Fasted mice treated with saline or scopolamine were allowed to eat solid food, slurry food or liquid food ad libitum, given placebo, or given liquid food by gavage. After 30 min, all animals were allowed to eat food pellets and observed for 30 min for the incidence and onset of convulsions. Scopolamine treatment caused convulsions only in the animals given solid food in the first 30 min; no convulsions were observed in the animals given slurry food, liquid food ad libitum, gavage, or placebo. When the animals that did not develop convulsions during the experiment were allowed to eat solid food, convulsions occurred. These findings indicate that complex mechanisms trigger scopolamine-induced convulsions in fasted animals eating solid food.