Physiology and Pharmacology
Year:2009 | Volume:13 | Issue:1|Papers Count:15

Introduction: Nitric oxide (NO) is a retrograde messenger in hippocampal synaptic plasticity which is involved in learning and memory processes. Previous studies revealed that hippocampal pyramidal cells contain NO synthase (NOS) enzyme, which produces NO and could be a promising target to evaluate the role of NO in brain cognitive functions. In this study, we conducted an experiment to assess the role of NO in passive avoidance learning by using a NOS inhibitor (L-NAME).Methods: Adult male Wistar rats (200-250 gr) were bilaterally implanted into the CA1 region of the hippocampus. Animals were subjected to behavioral tests one week after surgery. Rats received different doses of L-NAME (5, 10 and 15 mg/0.5ml/side) into the CA1 of hippocampus 25 min before training. Retrieval tests were performed in 3 different stages after training including working or immediate (immediately after training), short-term (90 min after training) and long-term (24 h after training) memories. Results: Our findings showed that pre-training injection of L-NAME 15 mg/0.5 ml/side significantly increased the number of step-through into the dark chamber for immediate memory, while decreased step-through latency for shortterm memory.Conclusion: These results suggest that hippocampal NOS inhibition impairs both immediate and short-term memory, but have no significant effect on long-term memory. Thereby hippocampal NO may affect early on learning and memory in passive avoidance task.

Introduction: Matrix metalloproteinase 2 (MMP-2) is one of the inflammatory mediators that is involved in the nociceptive processing and its production is regulated by many inflammatory factors such as nitric oxide. We studied the role of MMP-2 in the analgesia induced by an nNOS inhibitor.Methods: Considering that nitric oxide has many roles in pain processing, we studied the CSF levels of MMP-2 after hind paw formalin injection (50 ml, 2.5%) and neuronal nitric oxide synthase inhibition intrathecally. We also studied the effect of MMP-2 inhibitor on pain behavior and its role in the analgesic effect of neuronal nitric oxide synthase (nNOS) inhibitor.Results: Rats that received an MMP-2 inhibitor (30 mM) showed severe responses to formalin injection. Pain was reduced after nNOS inhibition. Prior to nNOS inhibitor injection, MMP-2 inhibition reduced the analgesic effects of nNOS inhibitor. Immunological studies showed that MMP-2 was increased in rats that received nNOS inhibitor.Conclusion: These data suggest a possible role for MMP-2 in the analgesia induced by nNOS inhibitors.

Introduction: recent studies have shown that normobaric hyperoxia (HO) can induce excitotoxicity and oxidative stress tolerance (ETT) in a variety of organs such as brain. In this study, we examined the effect of intermittent doses of normobaric hyperoxia (HO) on the neurological deficit and superoxide dismutase activity in the brain tissue of an animal model of Huntington’s disease. Methods: Rats were divided into 3 groups. The first group was exposed to HO intermittently (4h × 6 days; HO) and the second 2 main groups acted as controls, and were exposed to 21% oxygen in the same chamber (room air, RA) or discontinuously (4h × 6 days; InRA). HO and RA groups were immediately given 20 mg/kg of 3-nitropropionic acid for 6 days, Administration of 3-nitropropionic acid generates an animal model of Huntington disease, because Huntington disease is a neurodegenerative disorder. Then, ETT induced by HO was measured by the evaluation of neurological deficits such as string, limb withdrawal, inclined plane, beam balance test, and assessment of superoxide dismutase activity. Results: Our findings indicated that HO is involved in the induction of ETT. Pretreatment with HO significantly improved neurological deficits including string, limb withdrawal, inclined plane, beam balance test. Preconditioning with HO significantly increased superoxide dismutase activity.Conclusion: Although further studies are needed to clarify the mechanisms of excitotoxicity tolerance, pretreatment with HO seems to partly exert its effects through the enhancement of cell viability and superoxide dismutase activity.  

Introduction: The aim of this study was to obtain new insights into the possible relations between functional properties of slow concealed pathway and rate-dependent properties of the AV-node.Methods: Rate-dependent nodal properties of recovery, facilitation, and fatigue were characterized by stimulation protocols in one group of isolated super fused AV-Nodal rabbits (n=7). Small miniature lesions were made by delivering constant voltage (110 V-100 s) with unipolar silver electrode.Results: Fast pathway ablation significantly decreased facilitation and had no effect on fatigue and nodal refractoriness. The most important effect of fast pathway ablation was prolongation of the minimum conduction time. Conclusion: The FP-ablation revealed the presence of the concealed SP. Rate-dependent property of the node is dependent to dynamic interaction between concealed slow with slow pathway. The fast pathway was involved in the mechanism of facilitation.

Introduction: The role of insulin and its importance in ruminants are different form monogastrics. In this study, permanent hypoinsulinemia with different severities was induced by low, intermediate and high doses of streptozotocin in sheep (25, 50 and 75 mg/kg body weight, respectively).Methods: Twenty male lambs were divided into 4 treatment groups and were maintained individually. Three intravenous injections of streptozotocin were given. The whole experiment lasted 8 weeks, and injections were administered by the end of the third week. Blood samples were collected weekly by venipuncture at fasting state and 2.5 h post-prandial. Food and water intake, as well as weight changes were measured weekly. After slaughter, internal organs were weighed and urine samples were collected from the bladder.Results: Animals receiving the high dose of streptozotocin could not continue the experiment because of abnormalities. The intermediate dose caused significant decrease in fasted and post-prandial insulin concentrations as well as fasted leptin levels compared to control (P<0.05). This dose also induced a significant increase in blood glucose, triglycerides, cholesterol, total protein, blood urea nitrogen and keton bodies compared to control (P<0.05). These animals also showed diabetic hyperphagia and enhanced water intake in weeks after injection in comparison with the control group (P<0.05) but in spite of increased food intake, they could not gain more weight than controls. Urine sugar and protein levels were increased dose-dependently but these changes did not reach significance (P>0.05). Weights and indices of internal organs showed no difference among groups, but only carcass weight in the group of intermediate dose was significantly higher than other groups.Conclusion: Our results suggest a pivotal regulatory role for insulin in energy metabolism of ruminants by exerting two opposing effects; central catabolic and peripheral anabolic. These data are consistent with the findings in monogastric animals.

Introduction: ROMK channel is localized on the apical membrane of nephrons. Recent studies suggest that endocytosis of ROMK channels is important for regulation of K+ secretion in cortical collecting ducts. In this study, the effect of S362A mutation is examined on the membrane turnover and stability of ROMK2 channel when expressed in Xenopus laevis oocytes.Methods: oocytes were isolated by standard protocols using collagenase (Type 1A). Mutations of the cytoplasmic termini of ROMK2 were performed using the quik-change approach for site-directed mutagenesis. Xenopus oocytes were injected with cRNA encoding ROMK2 or S362A mutant 3 days prior to treatment with Brefeldin A added to the OR3 medium (+BFA) at the concentration of 25 μM or ethanol as BFA vehicle (-BFA). BFA inhibits the insertion of new proteins into the cell membrane. Two-electrode voltage clamp (TEVC) was used to measure oocyte ROMK-dependent currents and membrane potential. Data was analyzed using Student’s t-tests or ANOVA as appropriate.Results: Incubation of oocytes expressing ROMK2 channels in 25 mM BFA caused a reduction in the currents and membrane voltage. In oocytes expressing the S362A mutant, there was no decay in current and membrane voltage after 48 hours incubation with BFA at 25 mM. The fractional current for ROMK2 at 48h following treatment of oocytes with BFA was 0.24 ± 0.05 (n=24), which was significantly different from S362A mutant (0.96±0.05, n=24). Conclusion: These results show that the S362A mutation increases the general stability of ROMK and renders the protein resistance to endocytosis. This is consistent with the idea that there is an interaction between the C-terminal of ROMK2 and components of the endocytotic pathway. A functional PDZ domain (the S-E-V) plays a key role in determining the stability of ROMK.

Introduction: Previous investigations have indicated that the presence of BIO (6-Bromoindirubin-3-Oxime) in the culture medium of some cell types enhances both cell proliferation and viability. The aim of the present study was to investigate the effect of BIO on rat marrow-derived mesenchymal stem cells (MSCs) expansion in culture. Methods: In the present experimental study, bone marrow cells from 7 rats were plated in the presence of 0.05, 0.01, 0.1, 1 and 1.5 mM of BIO and expanded through 3 successive subcultures. During the cultivation period, the cultures were statistically compared in terms of indices of cell growth including the diameter and number of colonies, population doubling number (PDN) and the number of viable cells. Passaged-3 cells from all groups were examined for their differentiation capacity into bone and adipose cells.Results: According to our results, the largest colonies were formed in the cultures with 0.1 and 1 mm BIO with diameters of 1262.27 ± 43.96 and 1335.71 ± 19.16 micrometer, respectively (P<0.05). These 2 groups were also superior over other experimental and control groups in terms of colonies numbers. During 3 successive passages, significantly more PDN was occurred in 0.1 and 1 mM BIO-treated cultures compared with other experimental and control groups (P<0.05). Additionally, in these two BIO-treated cultures, the number of viable cells was significantly higher than that in other BIO-treated cultures as well as the control group (P<0.05). Alizarin red staining for bone and oil red for adipose cells indicated that the cells from all studied groups maintained the differentiation potential into bone and adipose cells.Conclusion: Our findings indicate that the presence of BIO in marrow cell cultures enhances the in vitro cell expansion and viability.

Introduction: There are many studies about the inhibitory effect of the esophageal distention (ED) on gastric motility. Recently, it has been shown that ED decreases gastric secretions. It is well established that the inhibitory effect of ED is mediated by activation of vago-vagal inhibitory reflex. However, there is not any investigation about the effect of the reflex on the gastric blood flow and release of gastric hormones. The aim of this study was to investigate the effect of esophageal distention (ED) on gastric blood flow and release of gastrin and somatostatin hormones. Methods: Seventy-nine male Wistar rats (175-230 g) were used in this study. The rats were deprived of food but not water 24 h before the experiments. Animals underwent tracheostomy and laparotomy under urethane anesthesia (1.2 g/kg, i.p.). A catheter was inserted in the stomach through the duodenum for gastric distension. The esophagus was cannulated with a balloon orally to distend distal portion of the esophagus (0.3 ml, 10 min). Saline was used for gastric distension (1.5 ml/100 g b.w., pH 7 and 37°C). Gastric blood flow was measured by a Laser Doppler flow meter. Serum gastrin and plasma somatostatin levels were assessed by RIA method. Vagotomy was carried out in a group to reveal the role of vagus nerve in this action.Results: ED reduced the blood flow of gastric proximal portion (P<0.001) but the antrum blood flow was unaffected by ED. Cervical vagotomy abolished the inhibitory effect of the ED on the proximal area blood flow. Serum gastrin and plasma somatostatin levels were unaffected by ED.Conclusion: Removal of the inhibitory effect of ED after vagotomy shows that the vagus nerve is involved in the inhibitory effect on gastric blood flow.

Introduction: Cupping therapy (hejamat) is one of the therapeutic methods used in traditional medicine that is still popular in many societies today. In spite of the advancement of science, we have less information on the traditional and alternative medicine including cupping. Study of the mechanisms of action of cupping makes the traditional medicine more convincing and therefore it can be used more easily for treatment. It can then be presented to the society with a more convincing scientific base. The aim of this study was to compare the biochemical, hematological and immunological factors of the blood obtained during the cupping with the venous blood.Methods: The study was performed on 56 healthy volunteer men aged between 20 and 40 years. At the beginning of the study, 16 ml venous blood sample was obtained from each volunteer. The cupping treatment was then given to the volunteers and another blood sample from cupping was taken for the comparison of biochemical, hematological and immunological factors. The biochemical factors were evaluated by Selectra auto analyzer, hematological factors by KX- 21 cell counter and sedimentation rate was measured by Westergreen method. Cytokines were measured by a sensitive sandwich ELISA kit (R&D system). Results: Analysis of the results showed significant differences in many of the biochemical, hematological and immunological factors between the venous blood and the cupping blood.Conclusion: Based on the results of the comparison between venous blood and cupping blood, the venous blood and cupping blood are different, both in components and immunologic response.

Introduction: In female rats sensitivity to antinociceptive treatment varies during different stages of the estrous cycle. The role of GABA through GABAB receptor in nociception has been established. The aim of the present study is to investigate the effect of intracerebroventicular injection of GABAB receptor agonist (baclofen) and GABAB antagonist (CGP35348) on pain sensitivity during different stages of the estrous cycle.Methods: Forty adult female rats weighing 200-220 g were used. Rats were maintained on 12 h reversed light/dark cycle, and standard temperature 22 ± 2°C. Food and water were available ad libitum. Pain sensitivity was evaluated by formalin test, performed by subcutaneous injection of 50 μl formalin solution (2.5%) into the hind paw in each stage of the estrous cycle. Data were analyzed by two-way ANOVA and Tukey test as post-hoc test. The level of significance was P<0.05.Results: Our data showed that baclofen significantly decreased pain sensitivity in all stages of estrous cycle (P<0.05). The analgesic effect of baclofen was significantly higher during metestruse and diestruse as compared to proestruse and estrus (P<0.05). CGP35348 significantly increased pain sensitivity in all stages of estrous cycle (P<0.05). The hyperalgesic effect of CGP35348 was significantly lower during metestruse and diestruse than proestruse and estrus (P<0.05). Administration of baclofen in pretreated rats with CGP35348 did not induce any significant change in pain sensitivity (P>0.05).Conclusion: We have demonstrated that GABA through GABAB receptor can modulate pain sensitivity during the estrous cycle.

Introduction: Blood hypercoagulability or thrombogenicity can be one of the main causes of cardiovascular diseases in the young population without traditional pathologic risk factors such as diabetes mellitus, hypertension or hyperlipidemia. The effect of aerobic exercise on coagulation and fibrinolysis has been studied extensively and the effectiveness of resistance exercise to increase the functional capacity of men has been documented. The aim of this study was to examine the effects of aerobic and combined aerobic-resistance exercise on the coagulation activity of healthy young men.Methods: 30 young healthy sedentary men (20 ± 5 years old) were randomly divided in 3 groups of aerobic, combined aerobic-resistance and nontraining control groups (n = 10 in each group). The aerobic training group subjects were engaged in a program including 10 sessions of exercise on cycle ergometer. Sessions were 24-min long with a submaximal intensity and were held 3 times a week. The combined group had 12 min of resistance exercise, followed by a 12 min aerobic exercise on cycle ergometer in each session.Results: The results revealed that PT was decreased and PTT was increased in both training groups compared to the control. Fibrinogen was decreased significantly in both training groups compared to the non-training control group.Conclusion: It was concluded that both submaximal aerobic and combined aerobic-resistance exercises, decrease coagulation system activity in young healthy sedentary men.