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Alcohol use disorder remains a major health problem. The mesocorticolimbic dopaminergic system, including the nucleus accumbens region and multiple neural circuits, is involved in its complex underlying mechanism. For instance, alcohol intake stimulates the central and peripheral renin-angiotensin system and increases angiotensin II levels, which predominantly affect angiotensin 1 receptors both in the periphery and in the brain. In this study, we aimed to investigate the effects of the intracerebroventricularly-administered angiotensin 1 receptor blocker telmisartan on the alcohol consumption of male Sardinian alcohol-preferring (sP) rats and on the alcohol-induced dopamine levels in the nucleus accumbens region in Wistar rats. Acute intracerebroventricular administration of telmisartan (100 nM) reduced the alcohol intake for 24 hours without affecting food and water consumption in sP rats. Acute intracerebroventricular injection of the opioid receptor antagonist naloxone (75 nM), tested as a reference compound, also reduced the alcohol consumption in sP rats; however, naloxone's effect lasted only for 30 minutes. In microdialysis experiments, telmisartan administered intracerebroventricularly did not change dopamine levels in the nucleus accumbens that had been induced by acute intraperitoneal alcohol administration in Wistar rats. According to these results, further studies are needed to elucidate the role of the renin-angiotensin system on alcohol use disorder pathophysiology.

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.

The aim of this study was to investigate the relationship between plasma glutamate, glutamine and gamma-aminobutyric acid (GABA) levels in female patients with major depression treated with S-citalopram or fluoxetine.The patients were assigned into S-citalopram (10 mg/day) or fluoxetine (20 mg/day) groups (n = 15 per group). The Hamilton and Beck Depression Inventory Scales were performed on all study participants, and blood samples were collected. The same procedures were repeated 10 days following the onset of therapy. Fifteen female healthy volunteers were also included in the study for the evaluation of normal plasma levels.The plasma GABA levels of the healthy volunteers were higher whereas those for glutamate and glutamine were lower than the day zero samples of the patients. An increase in plasma GABA levels and a decrease in glutamate and glutamine levels were observed on the 10th day of treatment. No difference was detected between the drug treatments.Our findings may suggest that GABA, glutamate and glutamine play a role in depression and that plasma GABA may be used as a biomarker for treatment control.

The posterior part of the hypothalamus plays a vital role in the homeostatic processes of the internal environment, including blood pressure and heart rate regulation, by means of γ-aminobutyric acid (GABA)ergic and glutamatergic neurotransmission. In this study we measured the extracellular levels of GABA and L-glutamic acid in the dorsomedial hypothalamic nucleus (DMH) and posterior hypothalamus (PH), following intracerebroventricular (i.c.v.) administration of bicuculline, a GABAA-receptor antagonist, in genetic absence epileptic rats from Strasbourg (GAERS), where heart rate, blood pressure, and EEG recordings were also collected simultaneously. The i.c.v. injection of bicuculline (0.3 nmol) produced no response in nonepileptic Wistar rats but caused an increase in mean arterial pressure in GAERS (P

Ethosuximide, 2‐ethyl‐2‐methylsuccinimide, has been used extensively for “petit mal” seizures and it is a valuable agent in studies of absence epilepsy. In the treatment of epilepsy, ethosuximide has a narrow therapeutic profile. It is the drug of choice in the monotherapy or combination therapy of children with generalized absence (petit mal) epilepsy. Commonly observed side effects of ethosuximide are dose dependent and involve the gastrointestinal tract and central nervous system. Ethosuximide has been associated with a wide variety of idiosyncratic reactions and with hematopoietic adverse effects. Typical absence seizures are generated as a result of complex interactions between the thalamus and the cerebral cortex. This thalamocortical circuitry is under the control of several specific inhibitory and excitatory systems arising from the forebrain and brainstem. Corticothalamic rhythms are believed to be involved in the generation of spike‐and‐wave discharges that are the characteristic electroencephalographic signs of absence seizures. The spontaneous pacemaker oscillatory activity of thalamocortical circuitry involves low threshold T‐type Ca(2+) currents in the thalamus, and ethosuximide is presumed to reduce these low threshold T‐type Ca(2+) currents in thalamic neurons. Ethosuximide also decreases the persistent Na(+) and Ca(2+)‐activated K(+) currents in thalamic and layer V cortical pyramidal neurons. In addition, there is evidence that in a genetic absence epilepsy rat model ethosuximide reduces cortical γ‐aminobutyric acid (GABA) levels. Also, elevated glutamate levels in the primary motor cortex of rats with absence epilepsy (but not in normal animals) are reduced by ethosuximide.

d -cycloserine (DCS), an FDA approved anti-tuberculosis drug has extensively been studied for its cognitive enhancer effects in psychiatric disorders. DCS may enhance the effects of fear extinction trainings in animals during exposure therapy and hence we investigated the effects of DCS on distinct behavioral parameters in a predator odor stress model and tested the optimal duration for repeated daily administrations of the agent. Cat fur odor blocks were used to produce stress and avoidance and risk assessment behavioral parameters were used where DCS or saline were used as treatments in adjunct to extinction trainings. We observed that DCS facilitated extinction training by providing further extinction of avoidance responses, risk assessment behaviors and increased the contact with the cue in a setting where DCS was administered before extinction trainings for 3 days without producing a significant tolerance. In amygdala and hippocampus, GluN1 protein expressions decreased 72 h after the fear conditioning in the traumatic stress group suggesting a possible down-regulation of NMDARs. We observed that extinction learning increased GluN1 proteins both in the amygdaloid complex and the dorsal hippocampus of the rats receiving extinction training or extinction training with DCS. Our findings also indicate that DCS with extinction training increased GluN1 protein levels in the frontal cortex. We may suggest that action of DCS relies on enhancement of the consolidation of fear extinction in the frontal cortex.

Cholestasis contributes to the genesis of fatigue through several mechanisms. Among these mechanisms, affected serotonergic neurotransmission is important in the pathogenesis of central fatigue. Previously, elevated levels of 5-hydroxyindole acetic acid (5-HIAA), the metabolite of 5-hydroxytryptamine (5-HT) and increased 5-HT(2) receptor density were demonstrated in the anterior hypothalamus and in the hippocampus of bile duct resected rats (BDR), respectively. The aim of this paper is to demonstrate evoked 5-HT release in selected brain regions like anterior hypothalamus and hippocampal CA1 regions of cholestatic rats using BDR rats as an experimental model for cholestasis. In this study, we analyzed the K+ evoked 5-HT and its metabolite 5-HIAA levels by using HPLC with electrochemical detection in the microdialysis samples collected from anterior hypothalamic and hippocampal CA1 regions of sham-operated and BDR rats (n = 6). The ratios of [5-HIAA] to [5-HT] following perfusion with 100 mM K+ artificial cerebrospinal fluid was used for the comparison of the evoked release of 5-HT. Locomotor activity was used to assess the signs of cholestasis associated fatigue in the BDR rats. The vertical and horizontal activity counts within 15 min were found to be decreased in the BDR rats compared to sham-operated rats (p < 0.05). Besides, the number of fecal boli (an index of emotionality) was also significantly fewer in the cholestatic rats (p < 0.05). No significant difference between the sham-operated and the BDR rats was detected in the basal 5-HT and 5-HIAA levels of anterior hypothalamus. K+ stimulation yielded a more profound increase in the [5-HIAA]/[5-HT] in the BDR rats (p < 0.05). The basal levels of 5-HT in CA1 region of the BDR rats was found to be lower than that of sham-operated group (p < 0.05), but no significant difference was observed in terms of evoked 5-HT release in both sham-operated and BDR rats. These findings imply the presence of affected serotonergic system in cholestasis.

Genetic absence epilepsy rats from Strasbourg (GAERS), a selectively inbred strain of Wistar rats, has been validated as an experimental model for human absence epilepsy. In this model, systemic administration of ethosuximide (ETX) was shown to reduce the spike and wave discharges (SWD). In this study, γ-aminobutyric acid (GABA) and L-glutamic acid levels in response to ETX injections (i.p., 100 mg/kg) were measured in the microdialysis samples collected from the ventrolateral thalamus (VLT) and the primary motor cortex (M1) area of Wistar rats and GAERS by using HPLC with fluorescent detection. Throughout the microdialysis procedure, continuous EEG recording was performed where ETX was shown to suppress the SWD activity. We demonstrated increased basal GABA levels in the M1 and VLT of GAERS, and ETX treatment did not produce any effect on higher GABA levels in the VLT, but suppressed the increased GABA levels significantly in the M1 of GAERS. All these findings denote the importance of corticothalamic circuitry and the role of increased GABA tonus in primary motor cortex and thalamus of GAERS. The primary motor cortex also seems to be involved in the SWD activity and ETX exerts, at least partially, its neurotransmitter effects through it. Keywords:: γ-aminobutyric acid, L-glutamic acid, primary motor cortex, thalamus, absence epilepsy

Fatigue associated with cholestasis may impair health-related quality of life. The pathogenesis of this symptom is largely unknown, but it has been suggested that central serotoninergic neurotransmission may be implicated and that serotonin 1A receptor agonists may yield improvement. The aim of this study was to study the central serotoninergic system, specifically the serotonin (5-HT)(1A) receptor-mediated pathway of serotoninergic neurotransmission, in a bile duct resection rat model of cholestasis. Fatigue was assessed in the forced swim test in sham and bile duct-resected rats. The serotonin behavioral syndrome, which includes hyperlocomotion, was assessed in both groups of rats after escalating doses of the 5-HT(1A) receptor agonist 8-hydroxy(di-n-propylamine)tetralin (8-OH DPAT). 5-HT(1A) and 5-HT(2) receptor densities were explored in four brain regions using a receptor-binding assay. Extracellular 5-HT and 5-hydroxyindoleacetic acid were measured via in vivo brain dialysis. Bile duct-resected rats spent more time floating in the forced swim test, and 8-OH DPAT decreased floating time in cholestatic rats (P < .01). Dose-response curves created with 8-OH DPAT for the serotonin behavioral syndrome were similar in bile duct-resected and sham-operated rats. 5-HT(1A) and 5-HT(2) receptor densities in most brain regions and extracellular serotonin levels were similar in both groups of rats. In conclusion, 5-HT(1A) receptor agonist-induced amelioration of fatigue in cholestatic rats may be nonspecific and not linked to reversal of the pathophysiology of fatigue associated with cholestasis; however, these data do not exclude a potential role of the central serotoninergic system in the evolution of fatigue.

Dorsomedial (DMH) and paraventricular nuclei (PVN) are two important hypothalamic structures involved in the central regulation of cardiovascular regulation. L-Glutamic acid and gamma-aminobutyric acid (GABA) were demonstrated to elicit cardiovascular responses when administered via intracerebroventricular injection or parenchymal microinjections into the hypothalamic nuclei, participating in central cardiovascular regulation. In this study the interaction between the DMH and the PVN were investigated by means of microinjection and microdialysis techniques in Sprague-Dawley rats. Stereotaxic surgery was performed for the insertion of intracerebral parenchymal microinjection cannula into the right DMH and microdialysis probe into the left PVN. After a recovery period of 3 days, the iliac artery was cannulated for monitoring pulsatile blood pressure and heart rate by means of pressure transducer connected to a polygraph. Microinjection of 50 pmol NMDA into the DMH was performed and microdialysis perfusates were collected simultaneously from the PVN in the conscious rat model. L-Glutamic acid and GABA levels were analyzed by an isocratic HPLC method with the aid of a fluorescent detector. Microinjection of 50 pmol NMDA into the DMH produced significant increases in mean arterial pressure and heart rate. NMDA microinjection into the DMH produced a significant increase in L-glutamic acid release in the PVN, but no significant change in GABA release was observed. These results may indicate that stimulation of the DMH by NMDA results in subsequent stimulation of the PVN.

Epilepsy affects homeostasis and autonomic nervous system functions. It has been thought that the dysfunction in the autonomic neural mechanisms could be a cause of sudden unexpected death in patients with epilepsy. The kindling model of epilepsy is considered to be an animal model for complex partial seizures with secondary generalization. The objectives of this study were to investigate the extracellular γ-aminobutyric acid (GABA), glutamate, noradrenaline and dopamine levels in the dorsomedial nucleus of the hypothalamus in non-epileptic and kindled epileptic rats and to explain some of the cardiovascular changes in the kindling model of epilepsy. Stimulation electrodes were stereotaxically implanted into the basolateral amygdala and electrical stimulation was applied 3 times a day at a constant current. The rats were then kindled to full stage 5 seizures. Microdialysis experiments were performed to demonstrate the neurotransmitter levels in the dorsomedial nucleus of the hypothalamus 3–5 days after being kindled. Decreases in noradrenaline and dopamine levels in the dorsomedial nucleus were detected in the conscious kindled animals. This finding is in agreement with prior findings that the noradrenergic system has a negative role in the process of kindling. The basal level of glutamic acid and GABA remained unchanged in the kindled group when compared to non-epileptic animals, and similarly, neither blood pressure nor heart rate responses to bicuculline or N-methyl-D-aspartate were affected by the acute kindled state. These findings suggest that the autonomic changes in kindling require further studies.

The dysregulation of hypothalamic–pituitary–adrenal axis and noradrenergic, serotonergic and glutamatergic systems are thought to be involved in the pathophysiology of post-traumatic stress disorder. The effect of selective M1 muscarinic receptor antagonist, pirenzepine on anxiety indices was investigated by using elevated plus maze, following exposure to trauma reminder. Upon receiving the approval of ethics committee, Sprague–Dawley rats were exposed to dirty cat litter (trauma) for 10 min and 1 week later, the rats confronted to a trauma reminder (clean litter). The rats also received intraperitoneal pirenzepine (1 or 2 mg/kg/day) or saline for 8 days. Noradrenaline (NA) concentration in the rostral pons was analyzed by HPLC with electrochemical detection. The anxiety indices of the rats subjected to the trauma reminder were increased when compared to control rats (p

This study shows the possible contribution of muscarinic receptors in the pathophysiology of post-traumatic stress disorder. Sprague-Dawley rats of both sexes were exposed to dirty cat litter (trauma) for 10 min and the protocol was repeated 1 week later with a trauma reminder (clean litter). The rats also received intraperitoneal fluoxetine (2.5, 5 or 10 mg/kg/day), propranolol (10 mg/kg/day) or saline for 7 days between two exposure sessions. Functional behavioral experiments were performed using elevated plus maze, following exposure to trauma reminder. Western blot analyses for M 1 , M 2 , M 3 , M 4 and M 5 receptor proteins were employed in the homogenates of the hippocampus, the frontal cortex and the amygdaloid complex. The anxiety indices increased from 0.63 ± 0.02 to 0.89 ± 0.04 in rats exposed to the trauma reminder. The freezing times were also recorded as 47 ± 6 and 133 ± 12 s, in control and test animals respectively. Fluoxetine or propranolol treatments restored the increases in the anxiety indices and the freezing times. Female rats had higher anxiety indices compared to males. Western blot data showed increases in M 2 and M 5 expression in the frontal cortex. Expression of M 1 receptors increased and M 4 subtype decreased in the hippocampus. In the amygdaloid complex of rats, we also detected a down-regulation of M 4 receptors. Fluoxetine and propranolol only corrected the changes occurred in the frontal cortex. These results may imply that muscarinic receptors are involved in this experimental model of post-traumatic stress disorder.

1 In the present study we have investigated the expression of muscarinic receptors in K562 erythroleukaemic cells and the effects of muscarinic agonist and antagonists on extracellular citrulline levels in these cells, as a marker of nitric oxide (NO) generation. 2 Muscarinic acetylcholine receptors (M(1)-M(5)) play key roles in regulating many diverse physiological processes. Recent studies suggest that muscarinic receptors mediate some cellular events in haematopoietic cells. Multiple subtypes of muscarinic receptors are expressed in different human cells. NO, a free radical and a signaling molecule, is involved in the regulation of many physiological functions and derived from certain nitric oxide synthases (NOS), which are related to muscarinic receptors. 3 In this study, the presence of M(2), M(3) and M(4) subtypes in K562, an erythroleukaemic cell line, was demonstrated by using the reverse transcriptase-polymerase chain reaction. Moreover, the generation of NO induced by carbachol, a non-selective muscarinic agonist, was investigated by using high-performance liquid chromatography to measure changes in extracellular l-citrulline levels. 4 We found that carbachol enhanced l-citrulline production in K562 erythroleukaemic cells. The effect of carbachol on l-citrulline production was antagonized by atropine and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP), while tropicamide had little effect. These results suggest that the muscarinic receptor M(3) subtype may mediate NO signaling in K562 erythroleukaemic cells.

Therapeutic drug monitoring (TDM) is a procedure in which the levels of drugs are assayed in various body fluids with the aim of individualizing the dose of critical drugs, such as cyclosporine A. Cyclosporine A assays are performed in blood. We proposed the use of the Takagi and Sugeno-type “adaptive-network-based fuzzy inference system” (ANFIS) to predict the concentration of cyclosporine A in blood samples taken from renal transplantation patients. We implemented the ANFIS model using TDM data collected from 138 patients and 20 input parameters. Input parameters for the model consisted of concurrent use of drugs, blood levels, sampling time, age, gender, and dosing intervals. Fuzzy modeling produced eight rules. The developed ANFIS model exhibited a root mean square error (RMSE) of 0.045 with respect to the training data and an error of 0.057 with respect to the checking data in the MATLAB environment. ANFIS can effectively assist physicians in choosing best therapeutic drug dose in the clinical setting.

Fluoxetine, as a serotonin re-uptake inhibitor augments serotonin concentration within the synapse by inhibiting the serotonin transporter. The contribution of amino acids has also been shown in depression. We hypothesized that fluoxetine exerts its actions at least in part by intervening brain signaling operated by amino acid transmitters. Therefore the aim of this study is to supply neurochemical evidence that fluoxetine produces changes in amino acids in cerebrospinal fluid of rats. Sprague-Dawley rats were anesthetized and concentric microdialysis probes were implanted stereotaxically into the right lateral ventricle. Intraperitoneal fluoxetine (2.5 or 5 mg/kg) or physiological saline was administered and the probes were perfused with artificial cerebrospinal fluid at a rate of 1 μl/min. In the chronic fluoxetine group, the rats were treated daily with oral fluoxetine solution or inert syrup for 3 weeks. The microdialysis probes were placed on the 21st day and perfused the next day. Fluoxetine was ineffective in changing the cerebrospinal fluid GABA levels at the dose of 2.5 mg/kg but produced a significant increase in the perfusates following injection of 5 mg/kg of fluoxetine (P < 0.05). Oral fluoxetine administration (5 mg/kg) for 21 days also elevated the CSF GABA levels by approximately 2-fold (P < 0.05). l-glutamic acid levels were not affected in all groups. These neurochemical findings show that fluoxetine, a selective serotonin re-uptake inhibitor affects brain GABA levels indirectly, and our results suggest that acute or chronic effects may be involved in beneficial and/or adverse effects of the drug.

Summary: Purpose: This study was planned to investigate the baroreflex responses (BRs) in kindled rats during seizure-free period to put forward new data on cardiac autonomic changes in epilepsy. Methods: Male Wistar rats were randomized into sham-operated (SO) and kindled groups where stimulation and recording electrodes were implanted stereotaxically into the basolateral amygdala and the cortex, respectively. For kindling process, rats were stimulated twice daily at their afterdischarge threshold current and accepted as being kindled after 10 grade 5 seizures. Six to 8 weeks after the establishment of the kindled state, mean arterial pressure (MAP) and heart rate (HR) were evaluated. BR was defined as the ratio of HR response to changes in MAP induced by i.v. nitroprusside (10, 25 μg/kg) or i.v. phenylephrine (10, 25 μg/kg). The sympathetic or parasympathetic component of the BR was evaluated in rats pretreated with atropine or atenolol where phenylephrine or nitroprusside was administered at 25 μg/kg. Results: Basal MAP and HR values were found to be similar in SO and kindled rats. Phenylephrine increased MAP more in the kindled group (p < 0.05), but the HR decreased similarly in both groups. Nitroprusside decreased MAP at similar rates, but the increase in HR was higher in the kindled rats (p < 0.05). BRs to phenylephrine and nitroprusside were abolished after pretreatment with atenolol and atropine, whereas phenylephrine- and nitroprusside-induced changes in MAP remained unchanged in both groups. Conclusions: These results may indicate that amygdaloid kindling affects BRs in long-term seizure-free periods.

To assess the impact of a rational pharmacotherapy (RP) teaching program during clinical pharmacology clerkship by analyzing the results of prescription audits (PAs) of the medical students. Collectively, we intended to observe the possible improvement of the students in their prescribing, problem solving and self-directed learning skills.At the beginning and end of the clerkship, the students were presented with cases of uncomplicated osteoarthritis to assess their prescribing skills; format and rationality were scored.A medical school in Turkey that teaches RP to the fourth-year students in clinical pharmacology clerkship.There were 94 students of the 2002-2003 academic year in three groups and a single group of students belonging to the previous academic year tested. Of those students from the previous academic year, 26 were also analyzed a year later to demonstrate the long-term impact of the training.Prescribing skills of medical students and their opinions about PA.Direct assessment via PA demonstrated that the scores for post-clerkship prescriptions were far better than those for pre-clerkship prescriptions in terms of format and rationality. Long-term assessment showed that the scores declined within a year following clerkship, but they were still higher than those of their pre-clerkship scripts. Analysis of the questionnaires revealed that the students were satisfied with PA. The majority of the students stated they had learned the general principles of RP and gained better prescribing skills, and they intended to apply most of the principles learned to their future professional lives. The script format scores of a retrospectively created PA-exempted group were significantly lower than those of the students to whom an established PA education was given.PA sessions were shown to be an easy and a useful method of both evaluating and reinforcing prescribing skills gained though problem-based RP education.

Epilepsy affects homeostasis and autonomic nervous system functions. It has been thought that the dysfunction in the autonomic neural mechanisms could be a cause of sudden unexpected death in patients with epilepsy. The kindling model of epilepsy is considered to be an animal model for complex partial seizures with secondary generalization. The objectives of this study were to investigate the extracellular gamma-aminobutyric acid (GABA), glutamate, noradrenaline and dopamine levels in the dorsomedial nucleus of the hypothalamus in non-epileptic and kindled epileptic rats and to explain some of the cardiovascular changes in the kindling model of epilepsy. Stimulation electrodes were stereotaxically implanted into the basolateral amygdala and electrical stimulation was applied 3 times a day at a constant current. The rats were then kindled to full stage 5 seizures. Microdialysis experiments were performed to demonstrate the neurotransmitter levels in the dorsomedial nucleus of the hypothalamus 3-5 days after being kindled. Decreases in noradrenaline and dopamine levels in the dorsomedial nucleus were detected in the conscious kindled animals. This finding is in agreement with prior findings that the noradrenergic system has a negative role in the process of kindling. The basal level of glutamic acid and GABA remained unchanged in the kindled group when compared to non-epileptic animals, and similarly, neither blood pressure nor heart rate responses to bicuculline or N-methyl-D-aspartate were affected by the acute kindled state. These findings suggest that the autonomic changes in kindling require further studies.

BACKGROUND/AIMS: Bacterial infections are known to trigger renal failure in patients with cirrhosis. However, the mechanisms for this process are unclear. The aim of this study was to investigate the role of endothelin-1 (ET-1) in a cirrhotic rat model with endotoxin induced renal failure by mixed ET-1 receptor antagonist, bosentan. METHODS: Cirrrhosis was induced by twice weekly intraperitoneal injections of CCl(4) together with phenobarbital in drinking water. Cirrhotic and non-cirrhotic rats were either pretreated with physiological saline or bosentan prior to administration of low dose endotoxin. Urine and blood samples were then collected within a period of 3 h for the estimation of ET-1, NO(3)(-)/NO(2)(-) levels ( nitric oxide metabolites: NO(x)) and renal function tests. RESULTS: Cirrhotic rats had higher ET-1 and NO(x) levels in comparison with non-cirrhotic rats. Endotoxin administration to cirrhotic rats led to the deterioration of the renal function, and elevation of plasma ET-1 and NO(x) levels. Bosentan pretreatment prior to endotoxin administration caused an increase in the urine volume and creatinine clearance of cirrhotic rats, but had no effect on Na(+) excretion. CONCLUSION: ET-1 has a significant role in endotoxin induced renal impairment in cirrhotic rats, and ET-1 receptor antagonism provides partial protection of the renal function.

In the present study, the effect of the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methylester (L-NAME), on the antishock actions of oxotremorine was investigated in rats subjected to hemorrhagic shock under urethane anesthesia. L-citrulline production in the AV3V region, as an indicator of nitric oxide (NO) synthesis, was assayed by high-performance liquid chromatography (HPLC) with fluorescent detection throughout the experiment. The rats were pretreated with either intravenous (i.v.) physiological saline or L-NAME (2.5 mg/kg) before bleeding. L-NAME potentiated the reversal of hypotension by oxotremorine (25 microg/kg, i.v.). However, oxotremorine either alone or in combination with L-NAME did not produce any significant change in 60-min survival rate at this low dose. Analysis of microdialysis samples collected from the AV3V region showed that L-citrulline concentration increased during bleeding and that this increase was abolished by L-NAME pretreatment. These results may suggest that nitric oxide production contributes to hypotension in rats bled to shock since nitric oxide levels in the AV3V region increased in response to bleeding and nitric oxide synthase (NOS) inhibition abolished this increase and potentiated the oxotremorine-induced reversal of hypotension.

Kindling, an animal model of complex partial seizures with secondary generalization, is performed by daily application of low-intensity electrical brain stimulation. The purpose of this study was to investigate the role of muscarinic M1 receptors on amygdala kindling in the rat. Bipolar nichrome stimulation and recording electrodes were stereotaxically implanted into the right and left basolateral amygdala. Extradural recording electrodes were also placed bilaterally in the skull over the cortex. Amygdala stimulation was applied twice daily at the current intensity of afterdischarge threshold. Seizure intensity was graded by using Racine's standard five-stage scale. In the first group of experiments, saline or pirenzepine (10, 25, 50 and 100 nmol), a muscarinic M1 receptor antagonist, was injected intracerebroventricularly 1 h before the electrical stimulation. In the second group of experiments, rats were kindled to full stage 5 seizures. After a recovery period, 50 nmol of pirenzepine was administered intracerebroventricularly to kindled animals. In the first group of experiments, none of the animals pretreated with the doses of 50 and 100 nmol of pirenzepine reached a stage 5 seizure. Pirenzepine significantly retarded kindling seizure development and increased the total number of stimulations required to reach the first stage 5 seizure. Afterdischarge duration was also reduced in the pirenzepine 10 nmol group as compared with that in the saline-pretreated group. In the second group, seizure stage and afterdischarge duration were not affected by pirenzepine in fully-kindled animals. The findings of this study suggest that muscarinic M1 receptors may have a critical role in the development of kindling epileptic activity, but not in already kindled seizures.

The purpose of the study was to investigate the in vivo metabolic pathway of 3-oxo-5-benzylidene-6-methyl-(4H)-2-(benzoylmethyl)pyridazine (substrate) in rats. Firstly its potential metabolites, i.e. N-dealkylation, ring scission of pyridazine and aromatic hydroxylation products, were synthesized and then the substrate was given orally (100 mg/kg) to male or female Wistar rats at a dose of 100 mg/kg to body weight. Blood samples were collected at 0, 1, 2, 4, 6 and 8 hours after administration of substrate and blood was centrifuged to obtain serum. The substrate and its potential metabolites were separated using a gradient HPLC method on a reverse phase system. This study revealed that 3-oxo-5-benzylidene-6-methyl-(4H)-2-(benzoylmethyl)pyridazine was not metabolized to the proposed metabolites and was present unchanged in the serum.

Agmatine (CAS 2482-00-0), an amine formed by decarboxylation of L-arginine, interacts with several targets like alpha2-adrenergic, imidazoline and N-methyl-D-aspartic acid (NMDA) receptors and besides it is involved in the nitric oxide mediated effects. It has also been proposed that it possesses vasodilator effects and increases glomerular filtration rate in rats. The aim of this study was to supply evidence for the effects of agmatine in a rat model of hemorrhagic shock and explain the possible mechanisms of action. The iliac arteries and veins of Sprague-Dawley rats were catheterized under urethane anesthesia and around 2 ml/100 g blood was withdrawn within 20 min until the mean arterial blood pressure was stabilized around 25 mmHg. The rats were either pretreated with physiological saline, yohimbine (an alpha2-adrenergic receptor antagonist) or L-arginine (a nitric oxide donor) intravenously before administration of agmatine (300 microg/kg). Agmatine restored blood pressure in rats pretreated with physiological saline where all rats survived. Pretreatment with L-arginine abolished the increase in blood pressure produced by agmatine and the 1 h survival rate decreased to 67% (p0.01). Yohimbine pretreatment also suppressed agmatine induced restoration of blood pressure; however, the survival rate was found to be 17% for 3 min. No statistically significant effect was observed in the heart rate responses. These results may suggest that agmatine may increase survival through alpha2-adrenergic receptors and restores blood pressure through nitric oxide and adrenergic mechanisms in rats bled to hemorrhage.