Quercetin protects radiation-induced DNA damage and apoptosis in kidney and bladder tissues of rats.

Ionizing radiation (IR) can induce cell damage and cell death through the reactive oxygen species generated by radiolytic hydrolysis. The present study was aimed to determine the possible protective effects of quercetin, a well-known antioxidant agent, against IR-induced bladder and kidney damage in rats. Sprague-Dawley rats were exposed to 8-Gy whole-abdominal IR and given either vehicle or quercetin (20 mg/kg, ip). Rats were decapitated at either 36 h or 10 days following IR, where quercetin or vehicle injections were repeated once daily, and kidney and bladder samples were obtained for the determination of myeloperoxidase and caspase-3 activities, an index of tissue neutrophil infiltration and apoptosis, respectively. Radiation-induced inflammation was evaluated through tissue cytokine, TNF-α levels. In order to examine oxidative DNA damage, tissue 8-hydroxydeoxyguanosine (8-OHdG) levels were measured. All tissues were also examined microscopically. In the saline-treated irradiation groups, myeloperoxidase and caspase-3 activities, 8-OHdG and TNF-α levels were found to be increased in both tissues (p < 0.05). In the quercetin-treated-IR groups, all these oxidant responses were prevented significantly (p < 0.05). The present data demonstrate that quercetin, through its free radical scavenging and antioxidant properties, attenuates irradiation-induced oxidative organ injury, suggesting that quercetin may have a potential benefit in radiotherapy by minimizing the adverse effects and will improve patient care.

Investigation into the role of the cholinergic system in radiation-induced damage in the rat liver and ileum.

It has been previously shown that acetylcholine (ACh) may affect pro-inflammatory and anti-inflammatory cytokines. The role of the cholinergic system in radiation-induced inflammatory responses and tissue damage remains unclear. Therefore, the present study was designed to determine the radio-protective properties of the cholinergic system in the ileum and the liver of rats. Rats were exposed to 8-Gy single-fraction whole-abdominal irradiation and were then decapitated at either 36 h or 10 d post-irradiation. The rats were treated either with intraperitoneal physiological saline (1 ml/kg), physostigmine (80 µg/kg) or atropine (50 µg/kg) twice daily for 36 h or 10 d. Cardiac blood samples and liver and ileal tissues were obtained in which TNF-α, IL-1ß and IL-10 levels were assayed using ELISA. In the liver and ileal homogenates, caspase-3 immunoblots were performed and myeloperoxidase (MPO) activity was analyzed. Plasma levels of IL-1ß and TNF-α increased significantly following radiation (P < 0.01 and P < 0.001, respectively) as compared with non-irradiated controls, and physostigmine treatment prevented the increase in the pro-inflammatory cytokines (P < 0.01 and P < 0.001, respectively). Plasma IL-10 levels were not found to be significantly changed following radiation, whereas physostigmine augmented IL-10 levels during the late phase (P < 0.01). In the liver and ileum homogenates, IL-1ß and TNF-α levels were also elevated following radiation, and this effect was inhibited by physostigmine treatment but not by atropine. Similarly, physostigmine also reversed the changes in MPO activity and in the caspase-3 levels in the liver and ileum. Histological examination revealed related changes. Physostigmine experiments suggested that ACh has a radio-protective effect not involving the muscarinic receptors.

The role of NO in the posterior hypothalamus in amygdala-generated pressor responses in conscious rats.

The nitrergic system modulates cardiovascular functions of the central nucleus of amygdala (CeA) and the posterior hypothalamus (PH) which are involved in the central regulation of the cardiovascular system. The aim of this study was to investigate the contribution of nitric oxide (NO) in the PH in eliciting cardiovascular responses produced through electrical stimulation (ES) of the CeA. Rats were implanted with a stimulation electrode and a parenchymal cannula system into the CeA and a parenchymal cannula or a microdialysis probe into the PH. The next day, the femoral artery was cannulated for haemodynamic measurement. The CeA was electrically stimulated to produce cardiovascular response. The nitric oxide synthetase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME; 400 nmol/100 nl) or artificial cerebrospinal fluid were injected into the PH or the CeA before the ES of the CeA. The dialysates were collected from the PH to determine the L-citrulline and the L-glutamic acid levels. L-NAME injection into the CeA but not to the PH suppressed the increases in the mean arterial pressure produced by the ES of the CeA significantly; however, heart rate was not affected by L-NAME injection into either the PH or the CeA. L-citrulline and L-glutamic acid levels in the PH were shown to be increased by the ES of the CeA. NO is involved between the PH and the CeA which has a considerable role in the central regulation of the cardiovascular system.

Comparison of rational pharmacotherapy decision-making competence of general practitioners with intern doctors.

OBJECTIVE: The aim of this study was to compare rational pharmacotherapy decision-making competency of interns (final-year medical students) who had received rational pharmacotherapy education (RPE), with their classmates at another medical school and general practitioners (GPs) who had not been exposed to RPE. DESIGN: A written, objective, structured clinical examination (OSCE), consisting of open and structured questions, was given to all participants. The participants were expected to make a treatment plan and prescribe for simple, uncomplicated beta-hemolytic streptococcal tonsillitis and mild-to-moderate essential hypertension patients, explain their proposed treatment plans and reasons affecting their drug choice. After the OSCE, a questionnaire to assess knowledge of the rational use of drugs was given to the participants. RESULTS: Fifty RPE(+) interns, 54 RPE(-) interns and 53 GPs participated in the study. Mean scores of RPE(+) interns were higher than those of GPs, which were in turn found to be higher than those of RPE(-) interns for all cases. The RPE(+) interns scored the highest regarding all components of rational pharmacotherapy process for all cases of both indications. However, participants in all groups had higher scores for the structured questions compared with the corresponding open ones for both diseases. Prescription analysis also revealed better results for RPE(+) interns regarding the number of drugs/prescription and treatment costs. CONCLUSION: The present study demonstrated that the final-year medical students (interns) markedly benefited from undergraduate RPE at the medical school in developing rational prescribing skills compared with their classmates from a medical school with traditional pharmacology education. Interestingly, they got higher scores than not only RPE(-) interns, but also than the GPs participating in this study, indicating the urgent need for continuous medical education programs in this field throughout the country for practicing GPs.

The role of nitric oxide in the reversal of hemorrhagic shock by oxotremorine.

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.

GABA and L-glutamic acid release in en bloc resection slices of human hippocampus: an in vitro microdialysis study.

The interaction of neurotransmitters has been a major interest in pathophysiological conditions like epilepsy. In vivo microdialysis has recently gained much validity in measuring neurotransmitter release in experimental animals. However, there is a paucity of data concerning its use in humans on the grounds of safety considerations. Microdialysis experiments were performed using the hippocampal head region removed from patients with medically intractable seizures, who underwent surgery for mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Following en bloc resection, the tissues were immediately transferred to the essential in vitro milieu. Slices were incubated in lactated Ringer's solution and microdialysis probes inserted into the slices were perfused with artificial cerebrospinal fluid (aCSF). When the K+ concentration of aCSF was elevated to 100 mM, GABA and L-glutamic acid levels increased by 293% and 177%, respectively. This method may serve as an experimental model for human brain, to throw more light on the interactions between GABA and L-glutamic acid in hippocampal tissues obtained from patients with MTLE-HS.

Investigation of extracellular L-citrulline concentration in the striatum during alcohol withdrawal in rats.

In this study, changes in striatal extracellular L-citrulline concentrations were investigated hourly for 5 h following alcohol withdrawal in chronic alcohol feeding Wistar rats. Alcohol (7.2% ethyl alcohol, v/v) was given to rats as modified liquid diet for 20 days. Signs of alcohol withdrawal appeared from the 1st h of alcohol withdrawal and the total alcohol withdrawal scores remained higher during the course of experiments. The mean of basal levels of L-citrulline in the microdialysis samples collected in conscious rat model from the striatum of control and alcoholized rats were found to be 1.28 +/- 0.48 microM and 0.35 +/- 0.08 microM, respectively. L-citrulline levels in the striatum of alcoholized rats increased by 4 folds significantly within 1 h following alcohol withdrawal. The increased striatal L-citrulline concentration was blocked by NG-nitro-L-arginine methyl ester (L-NAME; 60 mg/kg), a nitric oxide synthase inhibitor, pretreatment. Our results indicate an increased L-citrulline level in the rat striatum during early alcohol withdrawal and this situation may be related to an increased nitric oxide production.

Cardiovascular responses to NMDA injected into nuclei of hypothalamus or amygdala in conscious rats.

The nuclei of hypothalamus and amygdala have been shown to be involved in the central cardiovascular homeostasis. Recent studies suggest that glutamate-containing neurons have an important role in the regulation of the central cardiovascular function. In this study, we demonstrate the roles of the central nucleus of the amygdala and the paraventricular nucleus of the amygdala and the paraventricular nucleus or the dorsomedial nucleus of the hypothalamus in N-methyl-D-aspartate (NMDA) induced blood pressure and heart rate changes in conscious Sprague-Dawley rats. Intracerebroventricular or parenchymal injections of NMDA evoke increases in arterial pressure. The NMDA-induced elevations in blood pressure are more prominent when NMDA is administered into the dorsomedial nucleus of the hypothalamus. Microinjections of NMDA into the dorsomedial hypothalamus exert significant heart rate increases, whereas NMDA when administered into the paraventricular nucleus of the hypothalamus or into the central nucleus of the amygdala has no significant effect on the heart rate. The dorsomedial nucleus of the hypothalamus is found to be the most effective site in this respect. The present study provides strong evidence for the tonic glutamatergic influence on blood pressure and heart rate via NMDA receptors located within the dorsomedial nucleus and to a lesser extent via those located within the paraventricular nucleus of the hypothalamus.

Participation of NMDA and kainate receptors of paraventricular nucleus in cardiovascular responses to glutamate receptor agonist.

The nuclei of the hypothalamus have been shown to be involved in central cardiovascular homeostasis. Recent studies suggest that glutamate-containing neurons have an important role in the regulation of central cardiovascular function. We report first on the effects of intracerebrally injected NMDA and non-NMDA receptor ligands on blood pressure and heart rate in conscious Sprague-Dawley rats. In the second part, we describe the effect of blockade of NMDA or kainate receptors in the paraventricular nucleus on glutamate receptor agonist-induced blood pressure responses. Intracerebroventricular injections of L-glutamic acid, NMDA and kainic acid produced increases in mean arterial pressure. Kainic acid produced significant decreases in heart rate. Microinjection of DL-2-amino-5-phosphonopentanoic acid (APV; 25 and 50 nmol), a competitive NMDA receptor antagonist, into the paraventricular nucleus blunted the increases in the mean arterial pressure evoked by intracerebroventricular injections of NMDA (1 nmol), whereas microinjection of dinitroquinoxaline (DNQX; 20, 40 and 80 pmol), which acts as an antagonist at kainate receptors, failed to antagonize the cardiovascular effects of intracerebroventricular kainic acid (10 pmol). Microinjections of NMDA (100 pmol) into the paraventricular nucleus produced pressor responses, but kainic acid (5 and 10 pmol) failed to affect either mean arterial pressure or heart rate. These results suggest participation of the glutamergic system in cardiovascular regulation via NMDA receptors located within the paraventricular nucleus of the hypothalamus in rats.

Effect of pirenzepine, a muscarinic M1 receptor antagonist, on amygdala kindling in rat.

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.