Physiology and Pharmacology
Year:2010 | Volume:14 | Issue:2|Papers Count:15

Introduction: In order to study the alterations of beta 1 and 2 integrins mRNA level in rat lumbar spinal cord following the induction of chronic pain and its effect on the development of tolerance to morphine analgesia, we examined the level of expression of these genes in the presence of chronic pain, which is an inhibitor of morphine tolerance. We used induction of chronic pain alone and in combination with morphine administration.Methods: In order to induce tolerance to analgesic effect of morphine, morphine (15 mg/rat) was intrathecally (i.t.) injected to male adult Wistar rats twice a day for 4 days. Chronic pain was induced using formalin %5, 15 minutes before morphine injections during days 1-4. The analgesic effect of morphine was measured using tail flick test. Lumbar spinal tissues were assayed for the expression of beta-1 and 2 integrins using ‘‘semi-quantitative RT-PCR’’ and were normalized to beta-actin.Results: Chronic administration of morphine for 4 days developed tolerance to morphine analgesia. Concomitant induction of pain with morphine administration inhibited the development of tolerance to the analgesic. Induction of chronic pain, 15 minutes before morphine injections resulted in significant increases in beta-1 and 2 integrins mRNA levels. Furthermore, chronic pain alone also resulted in increased beta-1 and 2 integrins mRNA. Conclusion: Our results showed that, the induction of chronic pain prior to morphine administration, which is able to prevent morphine tolerance, increases the expression of integrins. Chronic morphine administration resulted in increases of beta 1 and 2 integrins mRNA level in lumbar spinal cord. It may be suggested that increases of beta-1 and 2 integrins mRNA is the result of the negative feedback of integrin inhibition by chronic morphine administration. Chronic pain is an enhancer of beta-1 and 2 integrins and its simultaneous presence with morphine administration results in increased beta-1 and 2 integrins and as a result prevents the development of morphine tolerance.

Introduction: The aim of this study was to assess the effect of Ca2+/calmodulin-dependent kinase Iiα (CaMKIIα) inhibitor (KN-93) injection into the locus coeruleus (LC) on the modulation of withdrawal signs. We also sought to study the effect of chronic morphine administration on CaMKIIa activity in the rat LC.Methods: The research was based on behavioral and molecular studies. In the behavioral study, we cannulated the LC with stereotaxic surgery and after 7 days of recovery, injections of KN-93, KN-92 (inactive analogue of KN-93) or DMSO (vehicle) was performed. Morphine and saline were injected in control groups. In the molecular study, we assessed the amount of phosphorylated CaMKIIa (pCaMKIIa) protein expression in LC nucleus using western blot technique.Results: Behavioral study; There was a significant difference in withdrawal signs between KN-93 and morphine dependent groups (P<0.05). No significant difference was observed between KN-92 and morphine dependent groups and also between DMSO and morphine dependent groups. Molecular study; Morphine and control groups and also morphine and naloxone groups showed significant differences in the level of pCaMKIIa (P<0.05). There was no significant difference between control and naloxone groups.Conclusion: Chronic morphine administration can increase the amount of CaMKIIa activity in LC nucleus and inhibition of this enzyme can decrease some withdrawal signs in dependent rats.

Introduction: Considering high prevalence of epileptic disease and considering that 40 percent of epileptic patients are resistant to drug therapy, it needs more researches to find new therapeutic ways. LFS is among the new methods for epilepsy treatments. One possible mechanism involved in the anticonvulsant effect of LFS is increased adenosine. Therefore, in this study the role of adenosine production from ATP by ectonucleotidase enzyme pathway in exerting the anticonvulsant effects of LFS were evaluated.Methods: Animals were kindled by electrical stimulation of perforant path in a rapid kindling manner (12 stimulation per day). One group of animals received LFS after kindling stimulation. In one another group, AOPCP a blocker of ectonucleotidase inhibitor was micro injected (50 micro molar) intra cerebro ventricular each day before LFS stimulation. Some group of animals were also received AOPCP (50 and 100 micro molar) but were not applied to LFS. Seizure behavior and electrophysiological parameters (including ADD and field potential) were recorded. Results: Like previous investigations, application of LFS, decreased all seizure parameters significantly. Microinjection of AOPCP had no significant effect on anticonvulsant actions of LFS. However microinjection of AOPCP at doses of 100 micro molar in animals that received just kindling stimulations, increased the seizure parameters significantly. Conclusion: The results show that adenosine production via ectonucleotidase enzyme pathway may has no role in anticonvulsant effects of LFS; however endogenous adenosine produced through this pathway has an important role in kindling development.

Introduction: Recent evidence has indicated that statins can reduce the incidence of both supraventricular and ventricular arrhythmias with various mechanisms. The primary goal of the present study was to determine direct protective role of simvastatin in modifying concealed conduction and the zone of concealment in a simulated model of atrial fibrillation (AF) in an isolated atrioventricular (AV) node in rabbits.Methods: Male Newsland rabbits (1.5-2 kg) were used in all experiments. Stimulating protocols (recovery, AF, zone of concealment) were used to study electrophysiological properties of the node in one group (N=8). All of the stimulated protocols were repeated in the presence and absence of different doses of simvastatin (0.5-10 mm). Results were shown as mean ± S.E.Results: Significant inhibition of the basic properties of the AV node was observed after the addition of simvastatin. Significant prolongation of Wenkebakh index (wbcl) from 138.7± 5.6 to 182.1± 6.9 and functional refractory period (FRP) from 157.7± 5.9 to 182.1± 6 msec at the concentration of 10 mM was observed. Maximum efficacy of simvastatin in atrial fibrillation (AF) protocol was observed at the concentration of 3.10 mM, that was accompanied with prolonged HH interval and increased number of concealed beats. Zone of concealment significantly increased at the concentrations of 1.3 and 10 mM.Conclusion: This study shows the protective effect of simvastatin in the prolongation of ventricular beats during atrial fibrillation. The effect of simvastatin in increasing AV-nodal refractory period and zone of concealment are probably the anti-arrhythmic mechanisms of this drug.

Introduction: Controversial results have been reported about the effect of morphine and stress on learning and spatial memory in rodents. There are very few studies about the effects of ultra low doses of morphine on memory. In this study, effects of acute administration of low and usual doses of morphine on memory formation and retention in the presence and absence of repeated stress were investigated.Methods: adult male Wistar rats (200-250g) were divided into 3 groups; A) Rats were trained for 4 constitutive days and then intraperitoneally received different doses of morphine (1mg/kg, 10mg/kg, 100mg/kg, 1mg/kg and 10mg/kg) 30 minutes before retention test on the 5th day. B) Animals experienced forced swimming stress 30 minutes before each training session for 4 constitutive days and memory retention was evaluated on the 5th and 12th days. C) Rats were treated like animals in-group B and then like group A. In all groups, retention tests were done without any excessive treatment on the 12th day. Escape latency and mean path length from the starting point to the platform on training days were considered as learning parameters, while time spent in the target quadrant on the 5th and 12th days was regarded as retention parameter.Results: Memory retention was decreased with 1 mg/kg and 10 mg/kg doses of morphine on the 5th day (P<0.001). Repeated stress led to decreased learning (P<0.001) and retention on the 5th and 12th days (P<0.05). In animals treated with both repeated stress and acute morphine (except for the dose of 1 mg/kg) retention decreased on the 5th day (p<0.001), while retention diminished for all groups on the 12th day.Conclusion: Morphine at usual dose of 10 mg/kg may cause memory retention impairment, by its inhibitory action on the opioidergic system. Surprisingly, morphine at ultra low dose (1 mg/kg) has the same effect and the excitatory action of opioidergic system may be responsible for this effect, however it needs further studies. Repeated stress in combination with morphine even at ineffective dosage could cause memory impairment in the Morris water maze, so the presence of both factors, can probably cause additive impairment of memory.

Introduction: Zinc is an essential rare element that plays an important role in synaptic plasticity and modulation of the activity of central nervous system and is involved in learning and memory. Increasing zinc intake may protect against conditions associated with zinc deficiency, such as diabetes. Some studies have revealed that zinc deficiency in diabetic subjects is due to hogher excretion or lower absorption of zinc in these subjects. Therefore, in this study, effects of various doses of zinc chloride on passive avoidance task were investigated in adult male Wistar rats without zinc deficiency.Methods: Male Wistar rats (200±20g) with streptozotocin-induced diabetes were used in this study. Rats were randomly divided into the groups that received ZnCl2 (30, 50, 70, 100 mg/kg/day) or the same volume of water (diabetic healthy control group) by oral gavage for two weeks. Each rat was then tested by Step-Down device once daily for 4 days. Memory, which was measured by the time that a rat stays on the stone bench, was measured 24h after the last trial (5th day).Results: The results showed that the use of ZnCl2 (30, 50, 70,100 mg/kg) for 2 weeks did not significantly affect passive avoidance learning and memory.Conclusion: These results indicate that ZnCl2 with doses that were administered in this study does not remarkably affect learning and memory process. This is probably because streptozotocin-induced diabetic rats have zinc deficiency and they require higher doses of zinc supplementation for compensation of zinc loss due to hyperzincuria.

Introduction: Aggressive behavior is a major issue in the field of mental health. Pharmacotherapy is often used for the treatment of violent individuals. A neurochemical system most consistently linked with aggression is the GABAergic system. The aim of the present investigation was to examine the effect of muscimol (GABAA agonist) 250 and 500 ng/rat and picrotoxin (GABAA antagonist) 1.5 and 3 ng/rat injection into central amygdaloid (ac) and medial amygdaloid (am) nuclei of amygdala on aggressive behavior.Methods: Fifty five adult male rats weighting 180 to 220 g were used. Cannulae were implanted into the ac and am nuclei of amygdala using stereotaxic method. Aggression was induced by applying 2 mA current every 3 seconds for 5 minutes. After the electrical shock, another rat was placed in the electroshock chamber, and the behavior of aggressive rat was evaluated in comparison to the normal one. Data were analyzed by one way analysis of variance ANOVA and Tukey as post-hoc test and Student T test. Level of significance was set at P<0.05. Results: Data showed that injection of muscimol (500 ng/rat) into the ac and am nuclei of amygdala significantly increased aggressive behavior (P<0.05). Injection of picrotoxin (1.5 ng/rat) into the ac nucleus of amygdala significantly increased the aggressive behavior, too (P<0.05). Furthermore, injection of picrotoxin (1.5 and 3 ng/rat) into the am nucleus of amygdala significantly increased aggressive behavior (P<0.05). Conclusion: It can be deduced that GABA system in the ac nucleus of amygdale is more potent than the am nucleus; and both ac and am nuclei of amygdala modulate aggressive behavior mediated by GABAA receptors.

Introduction: ghrelin is a potent orexigenic agent in rodents and humans. Some studies have shown that ghrelin participates in the adaptive response to weight loss and plasma concentration of ghrelin rises with dieting. On the other hand, weight loss and fasting is accompanied by increased levels of epinephrine and cortisol. In this study, we investigated the effects of epinephrine and cortisol on fasting-induced ghrelin secretion in rats fed different levels of their energy requirements.Methods: Forty-five male Wistar rats (300-350 g, 15 per group) were fed a diet containing 100%, 50% and 25% of their energy requirement for 10 days followed by 2 days of fasting. Animals were then anesthetized for carotid artery cannulation, which was used for injections and blood samplings. Rats received either 3 mg epinephrine (Ep)/Kg BW, 3 mg cortisol (Cor)/Kg BW, or a combination of these two (0.1 mg in 1 ml of PBS). Blood samples were collected before injections and 30, 60, and 120 min after injections.Results: mean plasma concentration of baseline ghrelin increased in the animals fed 50% food restriction (P£0.01). In 100% and 50% food restricted groups, fasting ghrelin levels fell after epinephrine and combination of epinephrine and cortisol injection (P£0.05). In contrast, the group that had 25% food restriction did not show any response to epinephrine and combination of epinephrine and cortisol (P>0.05), while the levels of the fasting ghrelin rose significantly after cortisol treatment (P£0.01).Conclusion: These results indicate that injection of epinephrine suppresses starvation-induced secretion of ghrelin in normal (100%) and starved (50%) rats. Ghrelin secretion response to epinephrine might be affected by weight loss as it does not seem to be suppressed in starved (25%) rats.

Introduction: Herbal medicine and medical plants such as Ziziphus vulgaris L. are widely used for treatment of diseases such as diabetes mellitus. In the present study, we have investigated effects of alcoholic extracts of Z. vulgaris fruit on serum glucose, triglycerides, LDL, HDL and activities of aminotransferase enzymes in streptozocin (STZ)- induced diabetic adult male rats.Methods: Herbal material was dried, ground and then extracted with ethanol using Soxhlet apparatus. The combined extract was evaporated to dryness and the residue was dissolved in water and used for treatments. Adult male rats were rendered diabetic by a single i.p. injection of STZ (65 mg/kg). Normal and diabetic rats were daily treated with the extract dissolved in 0.5 ml distilled water (0.25, 0.5,1 and 1.5 g/kg) administered by oral gavage for 2 weeks. After 2 weeks of treatment, blood samples were collected from retro-orbital sinus of rats (Stone method) and serum level of glucose, insulin, triglycerides, LDL, HDL and activity of aminotransferase enzymes were measured using enzymatic methods.Results: Continuous supplementation of the extract at the doses of 0.5, 1 and 1.5 g/kg in diabetic rats resulted in a significant decrease of fasting blood glucose and triglyceride levels after 14 days compared to the control group. Levels of LDL, HDL and activities of serum aminotransaminase enzymes, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), were not significantly changed in the extract treated group with respect to the control.Conclusion: Obtained results showed that Z. vulgaris contain effective antidiabetic compounds and maybe useful for treatment of diabetes mellitus.

Introduction: In the present study, the effects of oral morphine consumption in pregnant female rats on the amygdaloid complex development in the embryos were investigated. Methods: Female Wistar rats weighing 250-300 g (n=15) were divided into control (n = 8) and experimental groups (n = 7). The experimental group received morphine (0.05 mg/ml) in their tap water. On the 19th day of pregnancy, the animals were killed by chloroform overdose and their embryos were surgically taken out (57 control and 49 experimental embryos). Corticosterone concentration in plasma was determined by an ELISA method. The embryos were fixed in formalin 10% for 90 days, then their length and weight were determined and tissue processing, sectioning, Hematoxylin, and Eosin (H&E) staining were preformed. The cases (200 each) were evaluated and analyzed by light microscope and MOTIC software.Results: Our data showed that the length and weight of the embryos were not different among control and experimental groups. On the other hand, morphine consumption decreased the length and the area of the amygdaloid complex in the experimental group. In addition, the cell size was reduced in the experimental group, but the cell number was increased. Plasma corticosterone levels in control and experimental groups were not different. Conclusion: It could be concluded that oral morphine consumption during pregnancy could lead to amygdaloid growth retardation in the embryos of the pregnant rats demonstrated by the reduction in the length and area of the amygdaloid complex and the decrease of the cell size in the experimental group.

Introduction: It appears that some risk factors for coronary heart diseases (CHD) initiate their influence in the childhood period and their clinical complications start to take effect in adulthood. It is possible that adolescent active or sedentary boys, have other inflammatory silent risk factors of CHD, in addition to routine risk factors such as lipid profile. However, the scientific data available about the effects of aerobic exercise, physical fitness and nutritional status on the biochemistry indices of cardiovascular system (CVS) inflammatory response, such as homocysteine (HST), fibrinogen (FBG) and C-reactive protein (CRP) are contradictory.Methods: 42 volunteer boys from the city of Tehran (age: 10-14 years, BMI: 11-17 kg/m2 daily energy intake: 2477-2762 kcal) participated in the study and were divided in 3 groups of football players, swimmers and control group. The athletes had regular trainings for the last 3 year. Results: ANOVA-one way analysis of variance indicated that serum HST concentration in the swimmers (12.01 ±2.08 mmol/l) was significantly lower than HST levels of the football players (11.14 ± 2.8 mmol/l) (F=3.8, P=0.31). The FBG levels did not show any significant difference among athletic groups. Moreover, CRP concentrations of different groups were not significantly changed. Conclusion: Prolonged swimming training, BMI magnitude, initial physiological fitness level and the quantity of weekly training (not work intensity) could probably affect the biochemical markers (nontraditional risk factors) of cardiovascular system in young athletes.