Physiology and Pharmacology
Year:2007 | Volume:11 | Issue:2|Papers Count:12

Introduction: Assessing the variety and quality of the articles presented in the biennial national congresses of physiology and pharmacology is important to investigators in these fields. Analytic assessment of these presentations are of great use to know the stand points of physiology and pharmacology departments in different universities, and also can be informative for policy makers in higher education nation wide.Methods: In this research we have studied the presentations in the 10th to 17th congresses from different point of views such as general and specified scientific fields, and also the quantity of data production from various departments, universities, and cities. The total number of articles presented in the 10th to 17th congresses was 281,404, 529, 390, 723, 693, 719, and 687 respectively.Results: This study shows that the city Tehran is a center for productive universities. In addition, the majority of the studies have been systemic and molecular and cellular studies have not still found their expected stand point. Graduate studies seem to be the active generator for research in these fields and need more attention from policy makers. Overall there has been a steady quantitative growth in these presentations.Conclusion: Overall the research activity of Iranian physiologist and pharmacologists could be positively graded but needs great attention to remove the weak points and improve the strong ones.

Introduction: Previous studies have shown that the receptive field properties, spontaneous activity and spatio-temporal interactions of low-threshold mechanical somatosensory cells in the barrel cortex are influenced by C-fibers. In this study, we examined the effect of C-fiber depletion on response properties of barrel cortex neurons following experience dependent plasticity.Methods: In this study, extracellular single unit recording was performed on 154 barrel cortex neurons in 70 male Wistar rats (38-41days old). For depleting of C-fibers, neonatal rats received an intra-peritoneal injection of capsaicin solution (50 mg/kg) on the first neonatal day. For induction of experience dependent plasticity, all whiskers but D2 on the left muzzle, were plucked from first neonatal day. Neuronal ON and OFF responses were recorded in right barrel cortex following principal whisker (PW) and its caudal adjacent whisker (AW) deflection.Results: Whisker plucking increased PW-evoked ON responses both in capsaicin and vehicle treated rats (all P<0.05). In vehicle treated rats, AW-evoked ON responses were decreased in plucked animals (P< 0.05). Of particular interest, in capsaicin treated rats, AW-evoked ON responses were not decreased in plucked animals. Analyzing OFF responses showed similar result to ON responses.Conclusion: These findings indicate that c-fibers can modulate neuronal response properties following experience dependent plasticity in layer IV of barrel cortex.

Introduction: Development of brain edema following focal cerebral ischemia exacerbates primary ischemic injury. Blood brainbarrier (BBB) opening is an important part of edema named as vasogenic brain edema. In this study, quantitative alterations of BBB permeability is experimentally evaluated using transient focal cerebral ischemia in the rat.Methods: Two groups of male rats (ischemic and sham operated) were anesthetized with i.p. injection of chloral hydrate. In the ischemic group, middle cerebral artery (MCA) was occluded for 60 minutes using intraluminal filament method followed by reperfusion. In sham group all procedures, except MCA occlusion, were same as the ischemic group. An LV. injection of Evans blue (EB) was done 30 minutes after surgery. After 24 hours of reperfusion the neurological deficit score (NDS) was evaluated with a standard test. Then the animal was killed, the brain excised and prepared for quantitative evaluation of BBB permeability by detection of (EB) extravasations.Results: The mean of NDS in sham and ischemic groups were 1 and 2.25±0.31 respectively, indicating severe motor disabilities due to cerebral ischemia. In the ischemic group the concentration of EB in the right hemisphere (ischemic) was 12.48±1.94mg/g which was significantly higher than of the left hemisphere (1.44±0.39mg/g) or both hemispheres of the sham group. Furthermore, a direct correlation seems to exist between NDS and EB concentration ischemic rats.Conclusion: This study is indicating that quantitative detection of Evans blue extravagation technique is capable of measuring the alterations of BBB permeability in cerebral ischemia in the rat.

Introduction: Pheromones play a great role in the reproductive and social behavior of animals. The main sources of pheromones are urine and paracrine secretions. Through the neuroendocrine system, prolactin is a safe parameter to measure and compare the effects of ph erom ones on the sexual, maternal and also lactating behavior.Methods: Female rats were divided into 19 groups (n=8). To measure the plasma prolactin levels of rats, blood samples were collected and tested with prolactin RIA kits. Effects of sexual pheromones in the lactating period (3rd, 6th, 9th and 16th days after delivery), pregnancy priod (7th, 14th and 20th days) and lactating period (6th, 9th and 16th post-delivery days) on plasma prolactin level were surveyed. The effects of sexual pherornoneson the plasma level of Prolactin were determined using a special cage without any sensory stimulation interferences, such as visual, auditory and tactile senses.Results: Data showed a significant decline in plasma levels of prolactin following sexual pheromones administration (p<0.05). Significant increase in the prolactin plasma level was observed as the female rats were kept with a castrated male rat (p<0.05). During pregnancy period, prolactin level did not show any significant change in the first week of pregnancy with or without present male rat, but it showed a significant increase during the second and third weeks of pregnancy in the presence of male rat (p<0.01). The presence of male rat during the third, sixth and ninth days after delivery causes a significant increase in prolactin level (p<0.01) The females exposed to alien pups showed a significant decline in prolactin level compared those exposed to their own pups (p<0.05), but both groups showed same level of prolactin on the ninth and sixteenth days of delivery.Conclusion: These findings suggest that male sexual pheromones change plasma levels of prolactin in the pregnancy and lactating period and subsequently affect mating reproductive activities of rats.

Introduction: There is some evidence supporting the reduced activity of integrins following chronic administration of morphine. This reduction might play a role in morphine tolerance development. Manganese binds to the extracellular domain of integrins and makes them to be activated. The effect of integrins activation using manganese on tolerance development to the analgesic effect of morphine was investigated in this study.Methods: To induce tolerance to analgesic effect of morphine, morphine (15mg/rat) was injected intrathecally (Lt.) to male adult Wistar rats twice a day for five days. To investigate the effect of manganese, it was injected (20 nmol/rat-i.t.) I5 minutes prior to morphine injections during mentioned period. The analgesic effect of morphine (15mg/rat) was measured using tail flick test on day 6.Results: The results indicated thaHn animals which received both manganese and morphine during first 5 days; morphine induced a significant analgesia on day 6. Chronic administration of manganese did not change the pain threshold and morphine induced analgesia. Comparison of morphine analgesia following a single dose of morphine (15mg/rat) or chronic manganese+morphine, indicated that manganese did not have any effect on the morphine analgesia.Conclusion: Our results showed that, manganese administration prior to morphine is able to prevent morphine tolerance development. It seems that decreased activity of integrins following chronic administration of morphine plays a pivotal role in tolerance development to morphine analgesia. Further investigation needs to determine whether manganese effect is dependent on the integrins role in cell adhesions, or on their intracellular signaling pathways.

Introduction: Neurons in layer II and III of the somatosensory cortex in rats show high trequency (33±13Hz) of miniature excitatory postsynaptic currents (mEPSCs) that their rates and amplitudes are independent of sodium channels. There are some changes in these currents in neurodegenerative and psychological disorders, Regarding to well known roles of the neuromodulatory brain systems in these disorders, study the effects of these systems on the miniature currents provides data to understand more precisely pathogenesis of this disorders. Because cortical neurons receive very dense noradrenergic innervations, we examined effects of noradrenergic system on these currents.Methods: Whole cell patch clamp recordings were made on pyramidal neurons of the barrel cortex from brain slices that continuously super fused with artificial cerebrospinal fluid (ACSF) containing tetrodotoxin, sodium channel blocker and picrotoxin, blocker of the GABA receptors. Results: Application of noradrenalin significantly increased frequency and decreased amplitude of the mEPSCs. Using specific agonists and antagonists of the noradrenergic system, it was determined that the effects are mostly mediated by a1 receptor.Conclusion: Our results showed that noradrenergic system controls sodium channel independent synaptic transmission which can be of importance in regulation and induction of many physiological and pathophysiological conditions.

Introduction: The activity of Hypothalamus-Pituitary-Adrenal (HPA) axis is increased following inflammation due to its closed relation with immune system. This axis indicates an increased secretion of ACTH, and corticosterone during acute inflammation while little is known about its activity during chronic inflammation such as rheumatoid arthritis (RA). In this study we measured the products of HPA axis and their relation With IL-6 and hyperalgesia during rheumatoid arthritis.Methods: Fourteen Wistar rats were divided in two groups. RA was induced by subcutaneous injection of complete freund's adjuvant (CFA) to right hind paw of group I and the next group was considered as sham control. The levels of ACTH, corticosterone and IL-6 in blood samples were assessed using specific rat ELISA kits on zero, 6th and 21st days. Hyperalgesia was assessed using radiant hit instrument at the same days.Results: The results indicated a significant increase of IL-6 on days 6th and 21st in comparison with day 6. ACTH and corticosterone levels also significantly increased on the 6th day in the RA group in comparison with the control group, but there was no significant increase on the day 21st. Pain threshold was significantly decreased on the 6th day of intervention comparing to the day 0 in the RA group. On the 21st day of intervention, no significant hyperalgesia in the RA group was observed.Conclusion: The activation of HPA axis which is known to respond to IL-6, decreased during RA. ACTH and corticosterone secretion were not modulated during chronic inflammation in this study. On the other hand, long term RA symptoms such as hyperalgesia can be due to the effect of other modulators and independent on HPA axis and immune system.

Introduction: Previous studies have shown that low frequency stimulation (LFS) has an inhibitory effect on kindling acquisition. However, the mechanism of this effect has not been completely determined. In the present study, the effect of LFS of the perforant path on seizures induced by rapid perforant path kindling was investigated.Methods: Animals were kindled by electrical stimulation of perforant path, One group of animals (n=6) received LFS (0.1 ms pulses at 1 Hz, 200 pulse, and 50-150mA) after termination of each kindling stimulations. In control groups, animals received only kindling stimulations (n=8) or LFS (n=4). Basal field potential recording and paired pulse stimulations were done every day, before kindling stimulations.Results: Application of LFS significantly retarded the kindling acquisition and increased the number of stimulations to achieve different seizure stages [F(4,60)= 10.9, P<0.0001]. LFS also prevented increment of slope of field excitatory postsynaptic potentials and population spike amplitude during kindling (P<0.001) (There was 88.6±1.7% increment in fEPSP and 94±2.3% increment in PS in kindled group and 3.5±05% increment in fEPSP and 12.3±0.1% decrease in PS in kindled+LFS group). In addition, LFS significantly prevented the marked increase in early (10-50 ms intervals) and late (300-1000 ms intervals) paired pulse depression induced by kindling (P<0.01).Conclusion: According to obtained results, it may be suggested that LFS of perforant path has a significant antiepileptogenic effect on perforant path kindled seizures through inhibition of synaptic transmission in dentate gyrus. Meanwhile, LFS prevents compensatory increase in the paired pulse depression during kindling acquisition.

Introduction: Aluminum is known as a neurotoxic element which causes neurodegeneration, learning deduction and movement disorders. Aluminum ions in the brain cause serious problems such as Alzheimer, Parkinson and other degenerative diseases. On the other hand, Zinc is a dietary element essential for several biological processes, modulates neurotransmission in brain regions and associates with cognition. Apoptosis plays a role in many neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Imbalances of this metal, either excess or deficiency, can result in neuronal apoptosis. Here we have studied the effect of their co-administration on memory and motor activity.Methods: Zinc chloride (30 mg/kg/day) and aluminum chloride (600 mg/kg/day) were co-administered in drinking water of male rats for two weeks. Two criteria were assessed in behavioral tests: latency to enter and time spent in dark. Motor resistance and coordination were evaluated in movement studies.Results: Experiments showed that following 2 weeks co-administration of ZnCI2 (30 mg/kg/day) and AICI3 (600 mg/kg/day), passive avoidance memory and motor coordination have been improved (P<0.001).Conclusion: Results suggest that zinc chloride consumption with (30 mg/kg/day) dose, could have a significant effect on memory and motor coordination and could prevent the negative effect of AIC13on learning, memory and motor activity. Different mechanisms such as modulation of NMDA receptors and modulation of the entry of aluminum into the brain may be potentially involved in the observed effect of zinc.

Introduction: Based on the extensive application of Peganum harma/a (P.h) seeds in the Asian traditional medicine, we tried to investigate its possible anxiety effect.Method: The effect of P.h. extract inhalation was evaluated in adult male rats using elevated plus-maze apparatus. The humidity of prepared ethanol extract was 37%. Animals in different groups (n=6) received 2, 4, 6, 12 or 18gr/ml doses of the extract using Nebulizer. harmaline drug (0.13gr/ml) was used as positive control drug.Results: Compared with saline treated group, harmaline as the positive control significantly caused fear in rats as it was shown by increased time spent in closed arm of plus-maze (p<0.05). Also, ethanol extract of P.h was able to show anxiety effect at doses 6, 12 and 18mg/ml (p<0.05).Conclusion: Our data showed effective anxiety effect of ethanol extract of Peganum harmala. Its effect should be considered in the context of its extensive usage in the men daily life. More studies are required to elucidate its mechanism and site of action.