Physiology and Pharmacology
Year:2007 | Volume:10 | Issue:4|Papers Count:13

Introduction: The relation between morphine and nitric oxide release has been shown. Due to important role of nitric oxide in regulation of skin blood flow, the aim of this study was to investigate the effect of nitric oxide synthase inhibitor (L-NAME) and nitric oxide synthesis precursor (L-arginine) on skin blood flow of intact and morphine-dependent rats. Methods: Skin blood flow of hind paw was measured using Laser Doppler Flowmetry (LDF) technique. Animals became morphine dependent by a well established protocol. Results: Subcutaneous injection of L-arginine (10 or 20 mg/kg) respectively increased skin blood flow by 39% and 64% in intact rats and by 37% and 65% in morphine-dependent rats. There was no significant difference between blood flow in intact and morphine dependent rats. L-NAME (1 or 5 mg/kg) diminished skin blood flow of intact rats by 35% and 58.7% and skin blood flow of morphine-dependent rats by 29.1% and 60.5%, respectively. There was no significant difference between these two groups. The effect of Larginine was abolished by pretreatment with L-NAME in morphine-dependent as well as intact groups. Conclusion: Our results suggest that changes in the level of nitric oxide, cause the same skin blood flow alterations in both morphine-dependent and intact rats. More experiments are needed to elucidate the level of nitric oxide release in skin vascular system following dependency.

Introduction: Many people with amnesia would like to try herbal therapies. Ginkgo biloba is one of the most popular herbs which is used to treat amnesia. The beneficial effects of this plant, however, has not been scientifically assessed yet. Although, there have been some reports on the memory enhancement effect of Ginkgo biloba, the mechanism of its action is not yet explained well. Considering the role of glutaminergic system in learning and memory, the current study was intended to investigate the role of NMDA receptors in the effect of Ginkgo biloba intake on amnesia.Methods: The study used passive avoidance method to investigate the effect of dried extracts of Ginkgo biloba (40 milligram pills) on the memory span of male Wistar rats, suffering from MK801-induced forgetfulness (NMDA receptor antagonist). ANOVA was used to evaluate the results.Result: Ginkgo biloba was able to remove MK801-induced forgetfulness (P<0/001) indicating that the extract can affect learning and memory, using pathways other than glutaminergic system.Conclusion: The results might indicate that Ginkgo extract can be effective in treating non-acute amnesia caused by inhibiting NMDA receptors.

Introduction: Opiates cause dependency via affect on central nervous system. Locus coeruleus nucleus is a main group of noradrenergic neurons in the brain that plays an important role in the expression of opioid withdrawal signs. During opioid withdrawal, brain waves change in addition to physical and behavioral signs. In this study, we examined the effects of locus coeruleus electrical stimulation on brain waves of morphine dependent rats.Methods: Ten male Wistar rats were given intraplantar injections of increasing doses of morphine for 9 days. On day 10 after induction of anesthesia, electroencephalogram (EEG) recording was done. The EEG recording was also continued after intraplantar injection of naloxone. In the next step, rats were placed in stereotaxic apparatus and following the electrical stimulation of locus coeruleus, EEG was also recorded.Results: Naloxone Injection increased the power of delta waves (P<0.05) and decreased the power of theta waves (P<0.01). The power of alpha waves and beta waves had not significant changes following naloxone administration. Electrical stimulation of locus coeruleus, decreased the power of delta waves (P<0.01) and increased the power of alpha waves (P<0.05) , but did not change the power of theta and beta waves. The EEG total power increased during the withdrawal and decreased following electrical stimulation of locus coeruleus.Conclusion: The changes in EEG due to naloxone administration which reversed toward the basal level after electrical stimulation of locus coeruleus suggests that violence of the locus coeruleus activity by its electrical stimulation in withdrawal stage, results in a compensative reaction in order to attenuation the effects of hyperactivity of the locus coeruleus.

Introduction: Different mechanisms are involved in stress induced analgesia (SIA) and hyperalgesia (SIH). Repeated stress induces development of tolerance to SIA. The role of HPA axis and Gs signaling pathway in these effects are investigated in the current study.Methods: Forced swim stress (5 min/day) in water (20±1 °C) was employed to adult male Wistar rats (200-250 g). The nociceptive threshold was assessed using tail flick test. Adrenalectomized (ADX) rats were also subjected to stress tests. Oseltamivir was used to block Gs signaling pathway.Results: Stress produced analgesia for 1 h (p<0.001) and hyperalgesia during 3-24 h after its induction (p<0.05). Repeated administration of the stress caused tolerance development to SIA and increased SIH recorded at 24 h after each session (p<0.001). Oseltamivir couldn’t reverse the SIH. Dexamethasone produced hyperalgesia from 30 min (p<0.001) to 24 h after its administration (p<0.01). Repeated injection of dexamethasone increased the hyperalgesia recorded at 24 h after treatment (p<0.001). In ADX animals; SIA continued for 24 h (p<0.01). Adrenalectomy attenuated the chronic stress-induced SIA tolerance and eliminated SIH.Conclusion: SIH is suggested to be related to adrenal activity which also has a role in SIA tolerance. Upper parts of HPA axis seems to be responsible for SIA. Oseltamivir could not reverse the SIH. Therefore, the Gs signaling pathway activation by opioid system may not be responsible for SIH.

Introduction: Treatment of supraventricular arrhythmia includes wide range of medical interventions. Herbal remedies are suitable alternatives for synthetic drugs due to their availability, minimal side effects and lower price. Pharmacological studies and traditional medical literature point to the cardiovascular effects of the Artemisia absinthium L. from Compositae family of plants.Methods: In the present study we used Langendorff model of isolated heart of rats as an experimental model to determine the effect of various concentrations of methanolic extract of A. absinthium (3×10 -11 %W/V to 4× 10 -8 %W/V) on electrophysiological properties of isolated hearts.Results: Our results showed depressant effect of A. absinthium extract on Wenchebach Cycle Length (WBCL), AV Conduction Time (AVCT), Effective and Functional Refractory Periods (ERP & FRP) of the isolated heart.Conclusion: The results indicated potential antiarrhythmic effect of A. absinthium extract in treating supraventricular tachyarrhythmia.

Introduction: Previous studies have suggested that plants Avena sativa, Hypericum perforatum, Passiflora incarnata and Lavandula officinalis can affect nervous system and reduce neural excitability and pain. The aim of this study was to evaluate the effect of a mixture of these four plant’s alcoholic extract on morphine withdrawal symptoms.Methods: Experiments were performed on four animal groups of Wistar rats weighing 250-300 g (N= 7). For addiction induction, increasing doses of morphine were injected (Intraperitonealy (i.p.)) during nine days. After scientific identification, the plants were dried in room temperature and pulverized. Four plants powder were mixed with same proportion and then extracted using ethylic alcohol 70% by percolation method and then concentrated by rotary, and administrated at the dose of 400 mg/kg in all experimental groups. Morphine withdrawal syndrome symptoms include standing, stretching, jumping, Limbs shaking, blinking, ptosis, were recorded for 30 minutes.Results: Analysis of results showed a significant reduction of withdrawal symptoms in experimental groups (post and co -treated) in comparison with sham group.. Administration of extract cocktail prior to naloxone induced precipitation of withdrawal syndromes, reduced the expression of syndrome signs.Conclusion: It seems that administration of extract cocktail of these four plants inhibits both development and expression of morphine physical dependence symptoms. Considering the effects of different substances of above mentioned plants on excitability and anxiety mechanisms of the brain, the results of this study support the traditional application of these plants.

Introduction: Retinoic acid (RA) is a retinoid metabolite derived from vitamin A, which affects many metabolic and developmental processes. RA plays roles in physiological and pharmacological processes through regulating transcription of specific target genes.Peripheral administration of RA into human and animals decreases food intake, body weight and causes changes in biochemical blood parameters. Nucleus accumbens (NA) regulates the metabolism through hypothalamus and autonomic nervous system .In this study we investigated the effect of retinoic acid injection into NA on blood biochemical parameters such as glucose, triglyceride , cholesterol and lipoproteins level.Methods: Rats were anaesthetized by ketamin-xylazine (60mg/kg – 4mg/kg,ip) and implanted bilaterally by cannuli into the nucleus accumbens shell (AP=1.7mm and LA=0,8mm from bregma, DM=5,6mm from the scale). After one week recovery period, RA (1,5, 3 or 6 mg ) was injected daily (volume= 0.5 ml) for 4 days. Then animals were decapitated and the blood samples were collected. Serum levels of glucose, triglyceride and cholesterol were measured by spectrophotometry using commercial kits.Results: Data showed that centrally injected RA in nucleus accumbens caused decrement in serum level of cholesterol and HDL, but increased serum levels of glucose and triglyceride and didn’t change VLDL level.Conclusion: It seems that nucleus accumbens shell RA receptors are effective on metabolic reactions and serum levels of metabolites..

Introduction: Effect of tripolar TENS of vertebral column on slow and fast motoneurons (MNs) activity of soleus muscle was previously investigated. In this study for better differentiation of the behavior of slow and fast MNs, we exploited H-reflex recovery curve recording in two muscles of soleus and lateral gastrocnemius, respectively as the representatives of slow and fast muscles.Methods: 10 healthy non-athlete women aged 22.7±2.21 years participated in two (control and test) sessions. H-reflex recovery curve of soleus (slow) and gastrocnemius (fast) muscles were recorded before and 15 minutes after applying tripolar TENS (TENS frequency= 100 Hz and pulse width= 300 ms) on vertebral column. For recording the curve, rectangular paired stimuli were applied on tibial nerve (ISI= 40-520, frequency= 0.2 Hz, pulse width= 600  ms).Results: Our findings showed that maximum H-reflex recovery in gastrocnemius muscle appeared in shorter ISIs (240 ms), while in soleus muscle it appeared in longer ISIs (400 ms). H-reflex recovery curve amplitude slightly decreased after applying tripolar TENS. The comparison of H-reflex recovery curve of both soleus and gastrocnemius muscles either in control or test session did not show any significant difference (P>0.05).Conclusion: It is suggested that tripolar TENS excites not only the skin but also Ia and Ib afferents in the dorsal column. Synaptic interactions of these afferents in spinal cord cause the inhibition of type I MNs and facilitation of type II MNs.

Introduction: Alhagi camelorum belongs to the Leguminosae family is used in Iranian folk medicine to treat some gastric diseases. The present study was undertaken to evaluate the Alhagi camelorum aqueous extract for anti-ulcer activity in rats.Methods: Male Wistar rats were pretreated with the A. camelorum aqueous extract (150, 300 or 450 mg/kg of B.W., P.O.) before induction of gastric ulcer by water immersion restraint-stress at 20-22 °C (5 h) or before induction of the ulcer by ethanol 100% (1 ml/200g of B.W., P.O.). Negative control animals received saline (0.5 ml/100 g of B.W.).Positive control animals received ranitidine (60 mg/kg, P.O.).Results: The A. camelorum aqueous extract (ACE) protected rats against water immersion restraint-stress and ethanol-induced ulcers in a dose-dependent manner. In water immersion restraint induced ulcerated rat, the ACE increased pH and reduced gastric acid content. ACE did not show any signs of toxicity and mortality up to10 g/kg, P.O. in mice. Conclusion: The results suggest that A. camelorum aqueous extract can exert significant mucosal protection and antisecretory effects on gastric mucosa in rats.

Introduction: The Bed nucleus stria terminalis (BST) is a part of the limbic system. It was recently shown that chemical stimulation of the BST by L-glutamate elicited cardiovascular depressive responses. In the present study, we have investigated the possible cardiovascular role of the GABAergic receptors in BST by microinjection of its agonist and antagonists.Methods: Experiments were performed on 21 anaesthetized rats. Drugs were microinjected into the BST in volume of 50 nl using streotaxic apparatus. Blood pressure and heart rate were recorded before and throughout each experiment. The averages of maximum changes in the arterial pressure and heart rate were compared with control group and with its average in before injections using student t-test and paired t-test, respectively.Results: GABAA receptor antagonist, bicuculline met iodide (BMI, 1 mM), increased both arterial pressure (+14.2±3.08) and heart rate (+9.8± 2.5) (p<0.05). Muscimole, a GABAA agonist (5 mM), caused a significant decrease of the arterial pressure (-10.2 ±4.1) and heart rate (-20.3±9.40) (p<0.01). However, microinjection of phaclofen (5 mM), a GABAB receptor antagonist caused small unsignificant changes of the heart rate and blood pressure.Conclusion: GABAergic inhibitory neurons of the BST seems to cause decrease in the blood pressure and heart rate by GABAA but not GABAB receptors.