Croton hirtus attenuating streptozotocin-induced neuroinflammation in rats / 数字中医药（英文）

Objective@# The present study was aimed to investigate the neuroprotective effect of Croton hirtus (CH) extract against streptozotocin (STZ) in rats. @*Methods@#(i) The sub-chronic toxicity consisted of 24 adult rats of either sex weighing from 160 to 200 g were divided into four groups with six rats in each group. Rats in group 1 received Dimethyl sulfoxide (DMSO) mixed with saline; rats in groups 2, 3, and 4 received 100, 200, and 400 mg/kg of methanolic extract of CH (MECH) orally by gavage administration for 28 d, respectively. The functional observation battery and locomotor activity were graded as part of their neurobehavioral activity and the brain regions, including cortex and hippocampus, were analyzed for neuropathological abnormalities. (ii) The main research consisted of 30 adult male Wistar rats weighing from 160 to 200 g, which were divided into five groups and six rats in each group, including control (I), STZ (II), Donepezil (III), MECH (100 mg/kg, IV), and MECH (200 mg/kg, V) groups. Rats in group I received citrate buffer orally and DMSO mixed with saline for 14 d. Rats in group II received STZ via intracerebroventricular injection (3 mg/kg, bilateral ICV-STZ) on days 1 and 3 followed by DMSO mixed with saline for 14 d. Rats in groups III, IV, and V received STZ administration on days 1 and 3 followed by Donepezil [3 mg/(kg·d), p.o.] and MECH [100 and 200 mg/(kg·d), p.o.] for 14 d. Rats were tested for learning and memory parameters such as Morris water maze (MWM) and passive avoidance test (PAT). They were sacrificed after completing behavioural experiments; brains were harvested to estimate the acetylcholinesterase (AChE), lipid peroxidation (LPO), glutathione (GSH), and superoxide dismutase (SOD) by using UV-Visible Spectrophotometer; caspase-3 was evaluated by total fluorescence emission spectra; amyloid β (Aβ) levels were detected using enzyme-linked immuosorbent assay (ELISA); and histopathological examination was conducted in the CA1 region of the hippocampus.@*Results @# (i) The sub-chronic toxicity results revealed that open field test parameters including line crossing, rearing, entering the middle square, defecating, or urinating did not differ significantly in the MECH rats (P > 0.05). The histopathological observation did not show any lesions in the neuronal cells and inflammation in both the regions in MECH rats compared with control rats. (ii) The main study findings demonstrated that STZ-treated rats showed asignificant increase in impairment in learning and memory parameters (P < 0.001), the levels of AChE, caspase-3, Aβ (1-40 and 1-42), and LPO were increased significantly (P < 0.001), and significant decrease was found in the levels of SOD (P < 0.001) and GSH (P < 0.01). Moreover, neuronal damage was found in the hippocampus. In contrast, STZ-induced behavioural and biochemical impairments in rats were considerably decreased by treatment with MECH dose-dependently. @*Conclusion@#MECH significantly prevented the memory deficit induced by STZ due to antioxidant action. Restoration of cholinergic functioning may be the cause of behavioural improvement. Therefore, MECH may be able to treat cognitive disorders like Alzheimer's disease (AD).

Role of Brain Angiotensin-II in Development of Experimental Diabetic Nephropathy in Wistar Rats

Abstract The renin-angiotensin-aldosterone system (RAAS) plays a key role in diabetic nephropathy (DN). Angiotensin-II secreted during the RAAS pathway increases nephropathy. It stimulates oxidative stress which can quench nitric oxide. Reduced nitric oxide level aggravates Ang-II-induced vasoconstriction. Ang-II has also emerged as a central mediator of the glomerular hemodynamic changes that are associated with renal injury. Deletion of ACE2 is also noted due to increased Ang-II level which leads to the development of DN. We hypothesize that nephropathy caused by Ang-II in the periphery may be controlled by brain RAAS. ACE inhibitors and ARBs may show the renoprotective effect when administered through ICV without crossing the blood-brain barrier. DN was observed after 8 weeks of diabetes induction through alloxan. Administration of captopril and valsartan once and in combined therapy for 2 weeks, significantly reduced urine output, blood urea nitrogen, total protein in the urine, serum cholesterol, serum creatinine, serum triglycerides, and kidney/body weight ratio as compared to diabetic control rats. Further, combination therapy significantly increased the body weight and serum nitrate level as compared to diabetic control animals. However, increased ACE2 levels in the brain may reduce the sympathetic outflow and might have decreased the peripheral activity of Ang-II which shows beneficial effects in DN.

Evaluating the olfactory dysfunction and cognitive deficits induced by intracerebroventricular injection of Amyloid beta (1–42) in female C57BL/6 mice

Amyloid-β (Aβ) is a key pathological hallmark of Alzheimer's disease (AD), the most common form of dementiamajorly occurring in the geriatrics. Aβ accumulation is observed in the brains of AD patients and is reported toproduce long-term effects on cognitive functions leading to neurodegeneration, and subsequently, to AD. Olfactorydeficits are reported in AD and are proposed to be another consequence of these accumulations. The present studywas performed to primarily investigate the olfactory behavior and neurochemical changes in olfactory bulb uponintracerebroventricular (i.c.v) injection of Aβ (1–42) in female C57BL/6 mice. The study also assessed the cognitivechanges of i.c.v injected animals and recorded the subsequent changes in their hippocampus. All behavioral andneurochemical variations were noted separately on 7th, 17th, and 28th day after i.c.v injection. Results from thebehavioral analysis indicated prominent olfactory deficit from the 7th day. Reactive oxygen species levels increasedin both the tissues after Aβ injection. Neurotransmitter data showed that pathological accumulation of Aβ increasesglutamate levels in bulb and hippocampus. Additionally, histopathological evidence supported the neurochemical data.Data from the present study confirmed an olfactory dysfunction associated with AD and reported the neurochemicalchanges leading to these deficits in a non-transgenic model.

An Adapted Clinical Measurement Tool for the Key Symptoms of CLN2 Disease

Abstract Neuronal ceroid lipofuscinosis type-2 (CLN2) disease is a rare, autosomalrecessive,pediatric-onset,neurodegenerative lysosomal storage disease caused by mutations in the TPP1 gene. Cerliponase alfa (Brineura®), a recombinant form of human tripeptidyl peptidase-1, was recently developed as a treatment for CLN2 disease. In clinical trials, the primary end point to evaluate treatment effect was the aggregate score for the motor and language (ML) domains of the CLN2 Clinical Rating Scale, an adaptation of the Hamburg scale's component items that include anchor point definitions to allow consistent ratings in multinational, multisite, clinical efficacy studies. Psychometric analyses demonstrated that the ML score of the CLN2 Clinical Rating Scale and individual item scores are well defined and possess adequate measurement properties (reliability, validity, and responsiveness) to demonstrate a clinical benefit over time. Additionally, analyses comparing the CLN2 Clinical Rating Scale ML ratings to the Hamburg scale's ML ratings demonstrated adequate similarity.

Effects of intracerebroventricular injection of 7-nitroindazole on depression-like behaviors and nNOS expression in hippocampal of rats / 中华行为医学与脑科学杂志

Objective To evaluate the effect of intracerebroventricular injection of 7-nitroindazole (7-NI) on the depression-like behaviors in normal rats.Methods According to body weights,48 SD rats were randomly divided into normal group,model group,sham-operation group and 7-NI groups at different concentrations (n=8).The model group was treated with chronic and unpredictable mild stress.The 7-NI groups received intracerebroventricular injection with 7-NI solutions at different concentrations,once every 3 days for 3 times in total.The sham-operation group was injected with DMSO of the same volume.The rat behaviors were then subjected to the open field test (OFT).The hippocampal nNOS protein levels were detected by Western blot.Results Compared with the normal group((132.47±31.72) m),the total movement distances of model group ((15.04±8.61) m) and 200 nmol/0.5 μl surgery group((18.18± 11.82) m) decreased significantly (P＜ 0.05).Compared with the model group,such distances of sham-operation group ((107.33±20.35)m) and 7-NI groups(50 nmol/0.5 μl:(138.40±56.85)m,(86.97±36.20)m);100 nmol/0.5 μl:(86.97±36.20)m) increased significantly (P＜ 0.05).The normal group entered the central area significantly more times(2.25±2.05) than model group (0.25±0.46)and 200nmol/0.5μl 7-NI group (0.25± 0.46) did (P＜0.05),and the number of times entering the central area of the model group (0.25±0.46)was significantly lower than that of the sham-operation group (1.00 ± 1.07,P＜ 0.05) and 50 nmol/0.5 μl group (0.75 ± 1.16).Compared with the normal group ((46.53 ±41.16) s),the durations of stay in the central area of model group ((1.27 ± 1.92) s) and 200 nmol/0.5 μl 7-NI group ((1.53 ± 2.90) s) were shortened significantly (P＜0.05).Compared with the model group,the durations of stay in the central area of 100 nmol/0.5μl group ((36.54±67.80) s) was lengthened significantly (P＜ 0.05).Western blotting showed that the hippocampal nNOS protein levels of model group (0.43±0.11) and 200 nmol/0.5μl 7-NI group(0.56±0.08) significantly exceeded that of the normal group (0.04±0.02,P＜0.05).The levels of nNOS in sham-operation group (0.04 ±0.02) and 50 nmol/0.5 μl 7-NI group (0.22± 0.08),which were significantly lower than that of the model group (0.43 ± 0.11,P＜ 0.05),were similar to that of the normal group (0.04 ± 0.02,P＞ 0.05).Conclusion Intracerebroventricular injection 200 nmol/0.5 μl 7-NI solution results in depression-like behaviors and increased the expression of nNOS protein reflexively in rats.

Intracerebroventricular drug administration

Among the various routes of drug administration, perhaps the least studied is intracerebroventricular (ICV) administration. This route has been shown to be particularly useful in administering to the central nervous system (CNS) drugs that do not cross the blood-brain barrier readily. As such, the ICV route is a valuable option for providing therapeutic CNS drug concentrations to treat patients with CNS infectious and neoplastic diseases. This route of drug administration also has the advantage of minimizing systemic toxicity.

Effect of Intracerebroventricular Injection of Neuropeptide S on Pain and Anxiety Behaviors in Rats with Neuropathic Pain / 中国康复理论与实践

@#Objective To investigate the effects of intracerebroventricular injection of neuropeptide S (NPS) on pain and anxiety behaviors in rats with neuropathic pain, and explore the possible mechanism. Methods 40 male Sprague-Dawley rats were randomly divided into Sham-Vehicle group, Sham-NPS group, chronic constriction injury (CCI) group, Neuropeptide S low-dose group (NPSl group, 0.1 nmol/L) and Neuropeptide S high-dose group (NPSh group, 1 nmol/L), with 8 rats in each group. Pain-related behaviors, anxiety-related behaviours,and expression of NPS receptor (NPSR) in the left amygdaloid nucleus were measured on the 14th day via intracerebroventricular injection.Results Compared with the Sham-Vehicle group, the CCI group demonstrated significant pain and anxiety behaviors 14 days after operation (P<0.01), the NPSh group significantly relieved (P<0.01). And there was no significant difference between the NPSl group and the CCI group (P>0.05). Compared with the CCI group, NPSR expression in amygdaloid nucleus increased in the NPSh group. Conclusion NPS can dose-dependently relieve the pain and anxiety behaviors in CCI rats, which may be related with the increase of NPSR in amygdaloid nucleus.

Involvement of β3-adrenergic receptors in the control of food intake in rats

This study examined the food intake changes evoked by intracerebroventricular (icv) injection of a selective agonist (BRL37344, 2 and 20 nmol) or antagonist (SR59230A, 10 and 50 nmol) of β3-adrenergic receptors in 24-h fasted rats (adult male Wistar rats, 200-350 g, N = 6/treatment). The animals were also pretreated with saline icv (SAL) or SR59230A (50 nmol) followed by BRL37344 (20 nmol) or SAL in order to determine the selectivity of the effects evoked by BRL37344 on food intake or the selectivity of the effects evoked by SR59230A on risk assessment (RA) behavior. The highest dose of BRL37344 (N = 7) decreased food intake 1 h after the treatment (6.4 ± 0.5 g in SAL-treated vs 4.2 ± 0.8 g in drug-treated rats). While both doses of SR59230A failed to affect food intake (5.1 ± 1.1 g for 10 nmol and 6.0 ± 1.8 g for 50 nmol), this treatment reduced the RA frequency (number/30 min) (4 ± 2 for SAL-treated vs 1 ± 1 for 10 nmol and 0.5 ± 1 for 50 nmol SR59230A-treated rats), an ethological parameter related to anxiety. While pretreatment with SR59230A (7.0 ± 0.5 g) abolished the hypophagia induced by BRL37344 (3.6 ± 0.9 g), BRL37344 suppressed the reduction in RA frequency caused by SR59230A. These results show that the hypophagia caused by BRL37344 is selectively mediated by β3-adrenergic receptors within the central nervous system. Moreover, they suggest the involvement of these receptors in the control of anxiety.

The role of central mechanisms in the anti-inflammatory effect of amitriptyline on carrageenan-induced paw edema in rats

OBJECTIVE: The present study was designed to further investigate the effect of amitriptyline, a classical tricyclic antidepressant, on carrageenan-induced paw edema in rats. METHODS: First, amitriptyline was administered intraperitoneally (i.p.) at doses of 20, 40 and 80 mg kg-1, 30 min before subplantar injection of carrageenan. Second, amitriptyline was given intracerebroventriculary or intrathecally at doses of 25, 50 and 100 μg/rat, 30 min prior to carrageenan challenge. Third, the effect of adrenergic receptor antagonists such as propranolol (10 mg kg-1, i.p.), prazosin (4 mg kg-1, i.p.) and yohimbine (10 mg kg-1, i.p.) and an opioid receptor antagonist (naloxone, 4 mg kg-1, i.p.) on the anti-inflammatory effect of amitriptyline (40 mg kg-1, i.p.) was investigated. RESULTS: Our data confirm that intraperitoneally administered amitriptyline exhibits a marked anti-inflammatory effect on carrageenan-induced paw edema in rats 4 h postcarrageenan challenge (P < 0.001). Intracerebroventricular (i.c.v.) administration of amitriptyline also reduced the development of paw edema at 4 h postcarrageenan (P < 0.001), but intrathecal (i.t.) application of amitriptyline failed to alter the degree of paw swelling. Furthermore, the applied antagonists did not modify the anti-inflammatory effect of amitriptyline. CONCLUSION: These results support the view that amitriptyline has a considerable anti-inflammatory effect on carrageenan-induced paw edema in rats and suggest that at least a part of this property could be mediated through supraspinal sites. Moreover, it seems unlikely that the investigated adrenergic and opioid receptors have a significant role in this effect of amitriptyline.

Consequences of cerebroventricular insulin injection on renal sodium handling in rats: effect of inhibition of central nitric oxide synthase

In the present study, we investigated the effects of acute intracerebroventricular (icv) insulin administration on central mechanisms regulating urinary sodium excretion in simultaneously centrally NG-nitro-L-arginine methylester (L-NAME)-injected unanesthetized rats. Male Wistar-Hannover rats were randomly assigned to one of five groups: a) icv 0.15 M NaCl-injected rats (control, N = 10), b) icv dose-response (1.26, 12.6 and 126 ng/3 µL) insulin-injected rats (N = 10), c) rats icv injected with 60 µg L-NAME in combination with NaCl (N = 10) or d) with insulin (N = 10), and e) subcutaneously insulin-injected rats (N = 5). Centrally administered insulin produced an increase in urinary output of sodium (NaCl: 855.6 ± 85.1 Ä percent/min; 126 ng insulin: 2055 ± 310.6 Ä percent/min; P = 0.005) and potassium (NaCl: 460.4 ± 100 Ä percent/min; 126 ng insulin: 669.2 ± 60.8 Ä percent/min; P = 0.025). The urinary sodium excretion response to icv 126 ng insulin microinjection was significantly attenuated by combined administration of L-NAME (126 ng insulin: 1935 ± 258.3 Ä percent/min; L-NAME + 126 ng insulin: 582.3 ± 69.6 Ä percent/min; P = 0.01). Insulin-induced natriuresis occurred by increasing post-proximal sodium excretion, despite an unchanged glomerular filtration rate. Although the rationale for decreased urinary sodium excretion induced by combined icv L-NAME and insulin administration is unknown, it is tempting to suggest that perhaps one of the efferent signals triggered by insulin in the CNS may be nitrergic in nature.

Comparison of Alzheimer's disease animal model in BALB/c and Kunming mice by intracerebroventricular injection of β-amyloid / 军事医学科学院院刊

Objective:To compare the Alzheimer's disease model in two species of mice by intracerebroventricular injection of β-amyloid peptide 25-35(Aβ_(25～35)).Method:The step down test and Morris water-maze were used to investigate the influence of the mice's learning and memorizing ability after intracerebroventricular injection of β-amyloid.Results:Normal Kunming mice and BALB/c mice had no significant difference in step down test, but the space cognitive ability of Kunming mice was better than that of BALB/c mice. The learning response in step-down test and Morris water-maze is no influence in male, female BALB/c mice and female Kunming mice. Marked differences were observed in male Kunming mice in acquisition, performance and reversal of a place learning response in a Morris water-maze.Conclusion:The male Kunming mice is much better than female Kunming mice and male, female BALB/c mice in preparing Alzheimer's disease animal model by intracerebroventricular injection of Aβ_(25～35), and is the most suitable animal in this experiment.

Naloxone or Vagotomy Does Not Influence Centrally Octreotide-induced Inhibition of Gastric Acid Secretion in Rats / 华中科技大学学报（医学）（英德文版）

To investigate the effect of preceding naloxone injection into the third cerebroventricle or acute subdiaphragmatic vagotomy on the gastric acid secretion inhibited by the somatostatin analogue octreotide given by intracerebroventricular (icv) injection. The third ventricles were cannulated in male Wistar rats anesthetized with sodium pentobarbital. One week later, acute gastric lumen perfusion was carried out. The gastric perfusion samples were collected every 10 min and were fitrated by 0.01 mol/L NaOH to neuter. On the basis of subcutaneous injection of pentagastrin (G-5, 160 μ g/kg), icv injection of physiological saline (group A, n=20), icv injection of octreotide (0.05 μ g)(group B, n=20), icv injection of naloxone (2.5 μ g)+octreotide (0.05 μ g) (group C, n=20), acute subdiaphragmatic vagotomy+ icv injection of physiological saline (group D, n=20), or acute subdiaphragmatic vagotomy+icv injection of octreotide (0.05 μ g) (group E, n=20) were conducted. Before and after icy injection, 1-h total acid output (TAO) was determined and compared. The experimental data were expressed in change rate (%) of TAO. The change rates (%) of TAO were 4.60 % in group A, -20.35 % in group B, -18.06 % in group C, 5.01% in group D and -21.59 % in group E, respectively. Comparison of group B or C versus group A showed that P＜0.01 and comparison between the group E versus group D showed that P＜0.01. Whereas the differences between group C and group B, group E and group B were not statistically significant (P＞0.05 for all). The results indicate that the central inhibition of gastric acid secretion by octreotide may not be mediated by the endogenous opiate substance or its receptor and the peripheral pathway for icv injection of octreotide to suppress gastric acid secretion is via extra-vagus route.

El Sistema Nervioso Simpático Cerebral y la natriuresis inducida por la administración central de endotelinas

Se evaluó el papel de los receptores alfa1- alfa2- y beta-adrenérgicos cerebrales en la acción renal de las endotelinas (ETs). La administración intracerebroventricular (ICV) de ETs a ratas macho conscientes resultó en un incremento en la excreción urinaria de sodio a la 1, 3 y 6 horas del período de recolección de orina. La administración ICV de prazosin, un antagonista selectivo del receptor alfa1-adrenérgico, inhibió la respuesta natriurética de las ETs-ICV. Por el contrario, el pretratamiento central con yohimbina (un antagonista del receptor alfa2-adrenérgico) o con atenolol (un antagonista del receptor beta1-adrenérgico) no alteró significativamente la respuesta urinaria a la ET-ICV. Nuestros resultados demuestran que las endotelinas cerebrales se encuentran involucradas en los procesos que regulan el balance electrolítico e indican que el sistema nervioso simpático cerebral, a través del receptor alfa1-adrenérgico, participa en la acción natriurética de las ETs.

Experiments were conducted to investigate the role of brain the alpha1- alpha2 and beta-adrenergic receptors on the renal effects elicited by central injection of ETs. Cerebroventricular administration of endothelins (ETs) to conscious male hydrated rats resulted in an increase in urinary sodium excretion at 1, 3 and 6 hr period of urine collection. Central administration of prazosin (an alpha1-adrenergic receptor antagonist) inhibited the increase in sodium and urine excretion induced by ICV-ETs. Yohimbine (an alpha2-adrenergic receptor antagonist) or atenolol (an beta-adrenergic receptor antagonist) did not altered the urinary response to ET-IVT. Our results demonstrate a role for brain endothelin in the regulation of electrolyte balance and indicate that the sympathetic nervous system, through the alpha1-adrenergic receptor subtype, is involved in the natriuretic action of ETs.

Central N omega-nitro-L-arginine Methyl Ester Does not Influence Lithium-induced c-Fos and Conditioned Taste Aversion

LiCl at doses sufficient to induce conditioned taste aversion (CTA) causes c-Fos expression in the brain regions implicated in CTA formation. It has been reported that nitric oxide (NO) may play a role in CTA learning and LiCl increases both the synthesis and activity of NO synthase (NOS) in the brain. In this study, we examined the effect of central N omega-nitro-L- arginine methyl ester (L-NAME) on the brain c-Fos expression and CTA learning induced by lithium in rats. In the results, intracerebroventricular L-NAME given prior to lithium did not change either the lithium-induced CTA or c-Fos in the relevant brain regions. This suggests that the brain NO system may not be involved in the neuronal activation during lithium-induced CTA formation.

The dementia models induced by intracerebroventricular infusion of ?-Amyloid peptide in mice / 中国药理学通报

Aim To establish the dementia mice models induced by intracerebroventricular infusion of ?-Amyloid peptide and related measuring index. Methods The mice models were made by intracerebroventricular infusion of long fragment of soluble?-Amyloid peptide with micropump, intracerebroventricular injection of long soluble?-Amyloid peptide fragment and short insoluble ?-Amyloid peptide fragment,and intracerebroventricular injection of ?-Amyloid peptide combining with transforming growth factor. Results Compared with normal control, the learning and memory ability was decreased in all above model mice. the ChAT activity in both hippocampus and cortex of model mice decreased, the hippocampal neuron were depleted and the content of apoptosis associated protein Bal-2?BAX and p53 were increased. Conclusions All above mice models could be choose as the dementia models which were simulating the pathological charactoristics of the Alzheimer's disease.

Effects of Ginseng Saponin on the Stress-Induced Plasma Corticosterone Levels in Mice / 신경정신의학

OBJECTIVES: The present study was designed to investigate the effect of ginseng saponin and its major active metabolite on the HPA axis under acute stress-i.c.v. injection stress, and immobilization stress, and to examine whether nitric oxide is involved in the mechanism of ginseng saponin on the HPA axis under acute stress. METHODS: In the experiment to study the effect of ginseng on HPA axis during stress, various dose of GTS were injected intracerebroventricularly(i.c.v.) or intraperitoneally(i.p.). Plasma corticosterone levels were measured 30 min after the i.c.v. injection stress. Immobilization stress was applied for 30 min and then blood was cellected for the assays of plasma corticosterone levels immediately after the completion of immobilization stress. To determine the active ginsenosides that can affect the stressinduced plasma corticosterone levels, various dose of each gisendosides(Rb1, Rb2, Rc, Re, Rf, Rg1, 20(S)-Rg3, and 20(R)-Rg3) were injected i.c.v. or i.p.. In the experiment to determine the involvement of the nitric oxide in the inhibitory effect of ginseng on the HPA, NG-Nitro-L-arginine methyl ester(L-NAME) and ginsenosides were coadministered i.c.v. or i.p., and plasma corticosterone levels were measured 30 min after stress was applied. RESULTS: First, the present study showed that ginseng total saponin, ginsenoside Rg3(S form), and ginsenoside Rc administered i.c.v. attenuated the intracerebroventricular injection stress-induced increase in plasma corticosterone levels, and these effects were removed by nitric oxide co-injection. Second, ginseng total saponin and ginsenoside Rc administered i.p. attenuated the immobilization stress-induced increase in plasma corticosterone levels, but ginsenoside Rg3(S form) did not attenuate the immobilization stress-induced increase in plasma corticosterone levels. The attenuative effects of ginseng total saponin and ginsenoside Rc in the immobilization stress-induced increase in plasma corticosterone levels were not affected by L-NAME co-injection. CONCLUSION: This study suggests that ginseng saponin attenuated stress-induced increase in plasma corticosterone levels and these effects were mediated by different mechanisms according to the components of ginseng saponin, and routes of administration.

Effects of Kanagawa Hemolysin on Blood Pressure and Arterial Tone in Rats

Kanagawa hemolysin (KH), an exotoxin produced from Kanagawa phenomenon-positive Vibrio parahemolyticus, has been shown to possess various biological activities including hemolysis, enterotoxicity, cytotoxicity, and cardiotoxicity. The aim of this study was to investigate the effect of KH on the cardiovascular system and its mechanism, employing in vivo and in vitro experiments of the rat. Intracerebroventricular (icv) administration of 100 mHU KH produced a marked and continuous pressor effect (icv KH-pressor effect), and the icv pressor effect was not repeatable. However, intravenous (iv) injection of the same dose of KH induced a prominent depressor effect (iv KH-depressor effect). The icv KH-pressor effect was inhibited by acid-denaturation, while the iv KH-depressor effect was not. Simultaneous icv administration of the three agents (ouabain, diltiazem, or bumetanide: 10ng/kg each) significantly reduced the pressor effect. The icv KH-pressor effect was inhibited by treatment with iv phentolamine or chlorisondamine, but was not affected by iv candesartan. The iv KH-depressor effect was repeatable and was attenuated by treatment with iv NAME or methylene blue. In vitro experiments using isolated thoracic aorta, 10(-6) M phenylephrine (PE) and 50 mM KCl produced a sustained contraction. In rings contracted with either agents, KH showed relaxant responses in a concentration- dependent fashion and the relaxation (KH-vasorelaxation) was not dependent on the existence of the endothelium. The KH-vasorelaxation in the endothelium-intact rings contracted by PE was abolished by methylene blue treatment. In summary, the present findings suggest that in the icv KH-pressor effect the cation leak-inducing action of KH is implicated, which leads to the increased central sympathetic tone, that the iv KH-depressor effect results from the vasorelaxation via NO-guanylate cyclase system, and that the KH-vasorelaxation is independent of the endothelium and the guanylate cyclase system is involved in it. In conclusion, the mechanism of KH producing the icv pressor effect may not be identical to that of KH producing the iv depressor effect.

Effects of Endogenous Nitric Oxide Synthesis Inhibition on the Depressor Response to Intracerebroventricular Calcium

BACKGROUND: Aside from its well known peripheral antihypertensive effects, calcium also lowers blood pressure, when administered into the cerebral ventricle. The present study was aimed to determine whether the central depressor response to calcium is mediated by a stimulation of endogenous L-arginine-nitric oxide (NO) pathway. METHODA: Mean arterial pressure (MAP) and heart rate (HR) were continuously recorded from the femoral artery in anesthetized rats. Administration of calcium was performed into the right lateral cerebral ventricle. The effects of N G-nitro-L-arginine methyl ester (L-NAME) on the cardiovascular response to calcium were examined. RESULTS: Intracerebroventricular (ICV) injection of calcium consistently produced a decrease in MAP and HR. The depressor and bradycardiac responses to calcium showed a dose-dependent fashion. Pretreatment with a calcium channel blocker, diltiazem (1 micromol, ICV), attenuated cardiovascular responses to calcium. ICV infusion (1 microl/min) of L-NAME (200 microgram/kg and 20 microgram/kg/min for 60 min) increased MAP without significant changes in HR. Chronic ingestion of L-NAME (5 mg/100 ml in drinking water, 4 weeks) also increased the systolic blood pressure as compared with control. The depressor effect of ICV calcium was significantly diminished in acute or chronic L-NAME treated rats. CONCLUSION: These findings suggest that the central depressor response to calcium, at least in part, is NO-dependent.

Effect of brain angiotensin II receptor antagonists and antisense oligonucleotide on drinking and renal renin in rats

The physiological roles of brain angiotensin II in mediating water deprivation-induced drinking and in regulating renal renin release were assessed in male Sprague-Dawley rats. Specific AT1 receptor antagonists, losartan and SK 1080, and antisense oligonucleotide (AS-ODN) directed to AT1 receptor mRNA were intracerebroventricularly (i.c.v.) administered in conscious unrestrained rats. When water was given 20 min after i.c.v. injection of AT1 receptor antagonists in 48-h water-deprived rats, losartan and SK 1080 produced approximatly 20% and 50% decrease in 1-h water intake, respectively. In contrast, i.c.v. treatment of the AS-ODN to AT1 receptor mRNA for 24-h did not alter 1-h water intake in 24-h water-deprived rats, but prevented the increase in overnight water intake after 24-h water-deprivation. Six-day i.c.v. treatment of AS-ODN did not alter either the basal plasma renin concentration or renal cortical levels of renin and renin mRNA. The present results suggest that endogenous brain Ang II plays an important role in thirst and water intake through AT1 receptors, but further studies are required to elucidate its regulatory role in renal renin synthesis.

Pressor Responses to Intracerebroventricular Infusion of Hypertonic NaCl in Renal Hypertensive Rats

BACKGROUND: The sodium concentration in the central nervous system may play an important role in cardiovascular function and body fluid regulation. The purpose of this investigation was to examine the effects of intracerebroventricular (ICV) infusion of hypertonic NaCl solutions on the cardiovascular responses in normotensive and 2-kidney, 1 clip (2K1C) renal hypertensive rats. METHODS: 2K1C hypertension was made by clipping the left renal artery and were used 4 weeks later. Age-matched control rats received a sham treatment. Under thiopental (50 mg/kg, IP) anesthesia, both isotonic and hypertonic NaCl solutions (0.15 M, 0.6 M and 1.2 M) were ICV applied, while blood pressure and heart rate (HR) responses were continuously monitored. RESULTS: Central administration of hypertonic NaCl solution caused an elevation in mean arterial pressure (MAP) and HR in both normotensive and 2K1C hypertensive rats. The response magnitude in the blood pressure was positively correlated to the NaCl concentration in normotensive rats, while the pressor responses to hypertonic NaCl were comparable regardless of the concentration of NaCl in hypertensive rats. Despite of the HR responses were similar in between two groups, the magnitude of the MAP increases were more elevated in hypertensive than in normotensive control rats. Isotonic NaCl solution, when centrally applied, caused an elevation in blood pressure only in hypertensive rats. CONCLUSION: These results indicate that the central sensitivity to sodium chloride is altered in 2K1C renal hypertensive rats.