Physiology and Pharmacology
Volume:14 Issue: 4, 2011

Demyelination is one of the main causes of neurological disability. It is the end product of numerous pathological processes, multiple sclerosis (MS) being the most common cause. More than 70% of the MS patients suffer from optic disturbances. This disease commonly affects the optic pathway, particularly the optic nerves and chiasm. Several attempts have been made to produce a suitable model of demyelination in optic apparatus up to now. Local demyelination model was generated using direct injection of lysolecithin (LPC) into the optic chiasm of C57/BLJ6 mice without any undesirable distributions of gliotoxin into other brain structures. Histological and electrophysiological assessments of the processes of demyelination and remyelination in the animal model were done with specific myelin staining and visual evoked potential (VEP) recordings. In this study, both electrophysiological and histological results demonstrated that maximum level of demyelination was observed on day 7 post lesion and an incomplete yet significant remyelination took place on day 14 post lesion. Results showed a relatively rapid endogenous myelin repair in mice optic chiasm. Furthermore, this report might offer a new tool to address possible involvement of new origins of myelin-forming cells and subsequently their manipulation to promote myelin repair in the adult central nervous system

In the present work, spontaneous postsynaptic currents were assessed to investigate the postnatal development of excitatory postsynaptic currents in locus coeruleus neurons. In this study, AMPA and NMDA receptor-mediated spontaneous synaptic currents in the neurons of locus coeruleus were assessed using whole cell voltage-clamp recording during the first three weeks. The frequency and amplitude of NMDA sEPSCs and the frequency of AMPA sEPSCs were increased in the second and third postnatal weeks compared with these parameters recorded in the first postnatal week. However, the ratio of the AMPA to NMDA current frequency and amplitude was constant until the 3rd postnatal week. These findings suggest that a vast majority of nascent glutamatergic synapses express both functional AMPA and NMDA receptors in the postnatal locus coeruleus, so that AMPA/NMDA sEPSCs remained constant during this period.

Human embryonic stem cells (hESCs) are pluripotent cells that can proliferate and differentiate to many cell types. Their electrophysiological properties have not yet been chracterzed. In this study, the passive properties (such as resting membrane potential, input resistance and capacitance) and the contribution of delayed rectifier K+ channel currents to the membrane conductance of hESCs was investigated. hESC (Royan H6 line) was used in this study. Cells were cultured with feeder free culture method. To study the electrophysiological properties of these cells, we used whole cell patch clamp technique in a voltage clamp mode. Ionic currents were recorded by stimulating the cells with depolarizing steps from -90 mV to +50 mV. For pharmacological determination of these currents, potassium channel blockers such as tetraethyl ammonium (TEA; a delayed rectifier K+ channel blocker) and 4-aminopyridine (4-AP; as an A-type K+ channel blocker) were used. The resting membrane potential of hESCs was -8.66± 0.87 mV, the input resistance was 11.943 ± 0.23 MΩ and the membrane capacitance was 1.46 ± 0.55 nF. In voltage clamp experiments, some outward currents were recorded in hESCs that were progressively increased with positive voltages. These outward currents were inhibited by TEA but not 4-AP. These channels did not show inactivation and their current were recorded from -60 mV. The mean conductance of these channels was 11.81 ± 0.45 pS at -60 mV and 141.4 ± 10.97 pS at +50 mV. There were no inward currents in hESCc.

Pain research using animal models is related to ethical concerns, so invertebrates and insects have been recommended by researchers. In the present study, the nociceptive and antinociceptive effects of capsaicin, aspirin, morphine and chili extract were examined using fruit fly (Drosophila melanogaster) as an alternative for rodent pain model. Stage 3 of larvae and adult state of Drosophila were used. Threshold and maximum reactions were recorded in thermal nociception (using Hot plate) and chemical nociception (Writhing test) at various concentration of acetic acid, capsaicin and chili hydro alcoholic extract. Rolling movement responses were recorded in separate groups (n=7). In adult Drosophila, latency for heat tolerance on hot plate was recorded (n=10), and the effect of morphine and aspirin at different concentrations on pain were examined. Increasing the temperature, acetic acid, capsaicin and chili extract concentration, attenuated the rolling movement in larvae. In adult drosophila, increasing the temperature, diminished tolerance latency on hot plate. In this animal model, increasing the morphine and aspirin concentration diminished responses to pain stimulus. According to our results, it can be suggested that Drosophila melanogaster can be used as a model for investigation on pain physiology and antinoiciception. Painless channel (closest vertebrate homolog of TRAP1 channel) maybe required for thermal and chemical nociception in drosophila. Similar to mammals, treatment with morphine and aspirin may exert these effects through Gi and cox2 respectively.

Intravenous general anesthetic agents are among the most important and widely used anesthetic drugs in the clinical practice. Many pharmacological studies have shown that potentiation of GABA and glycine on their receptors is the most plausible mechanism. Nevertheless, there is limited information on the effects of co-administration of two or more of these agents. However, experimental models for investigation of optimized drug combinations to have maximum effects on the receptors, have certain limitations and are both time consuming and expensive. One method to optimize drug combinations is the use of artificial neural network, in which the response optimization is performed by using experimental results. In this research, artificial neural network has been used to model a function with seven input and one output variants. Each input variant represents one of the intravenous general anesthetics including thiopentone, methohexitone, pentobarbitone, propofol, etomidate, saffan and ketamine and the output variant is the effectiveness of these drugs on glycine receptors. Results of the present study show that maximum potentiation of the tested drugs on glycine receptor are around 1500%, which can be achieved under certain drug concentrations, while maximum potentiation that has been obtained in experimental models by combination of propofol or saffan and by combination of thiopentone and pentobarbitone has been around 600% and 640%, respectively. In order to evaluate and validate the calculated results, experiments are recommended to be performed with the proposed combinations and concentrations.

In the present study, potential differences between the effects of L-carnitine (LC) and acetyl-Lcarnitine (ALC) on ischemia/reperfusion (I/R)-induced myocardial infarction size were investigated. Male Wistar rats were randomly divided into five groups and then anesthetized by sodium pentobarbital. Hearts of the animals were removed and quickly mounted on a Langendorff apparatus and perfused under constant pressure by a modified Krebs-Henseleit (K/H) solution. The hearts were perfused during 30 min regional ischemia followed by 120 min reperfusion by normal K/H solution (as control) or enriched solution with 1.5 and 3 mM LC (groups 2 and 3) or ALC (groups 4 and 5). At the end of the reperfusion cycle, 0.25 % evans blue solution was infused to stain the non-ischemic area, then the hearts were cut into slices and incubated by triphenyltetrazolium chloride solution and fixed by formalin. The infarction size was determined by using a computerized planimetry package. The infarct size after perfusion of isolated hearts with 1.5 (26±4.5%) and 3 mM LC (20±4 %) showed a significant reduction compared to the control value (45.6±3.4 %, P<0.01 and P<0.001, respectively). The same concentrations of ALC significantly lowered myocardial infarction size to 23.8±4 % (P<0.01) and 15.8±2.9 % (P<0.001), respectively. When the effects of similar concentrations of LC and ALC on the infarction size were compared, there was no statistically significant difference (p>0.05). Among the potential protective mechanisms of the agents, increase of glucose oxidation, reduction of lactate production, toxic fatty acid metabolites and removing free radicals from the myocytes seem to be more relevant. The results of this study demonstrated the protective effects of LC and ALC against I/R injuries by reduction of infarct size in isolated rat hearts without any important difference between the agents.

The magnocellular neurons (MCNs) of the supraoptic nucleus (SON) play a crucial role in control of physiological and pathophysiologiccal condition due to two peptides that they synthesize, i.e. Oxytocin (OXT) and Vasopressin (AVP). The activity of MCNs is regulated by a variety of excitatory and inhibitory inputs. Opioid receptors are one of the important receptors in SON synapses. The aim of the present study is to evaluate the effect of acute morphine application on SON synapses and AVP release in rats. In this study, whole cell patch clamp recording of neurons in rat (70-100 g, 3–4 weeks old) brain slice preparations consisting of SON was used to investigate the effect acute of lowest effective dose of morphine (25μM) administration on spontaneous inhibitory and excitatory post synaptic currents (sIPSCs and sEPSCs) in MCNs. Also, AVP levels were measured in blood samples of rats using ELISA technique after the Morphine injection (30 mg/kg, ip). Bath application of morphine produced an increase in sEPSCs and a decrease in sIPSCs frequencies. Measurement of plasma AVP revealed an increase in hormone levels 45 min after systemic administration of morphine. P-values of less than 0.05 were considered statistically significant. It is suggested that acute administration of morphine stimulates the MCNs and AVP secretion.

Glial activation and secretion of cytokines at the spinal level is known as part of chronic pain pathogenesis. Although changes in TNFα at the supraspinal level are reported during chronic pain, its exact role and site of action remain to be elucidated. We investigated the effect of microinfusion of TNFα into the LC in a rat model of neuropathic pain. Male Wistar rats were cannulated in the LC. The cannula was connected to an Alzet mini-osmotic pump, which was filled by the drug (vehicle, TNFα or TNFα-antibody) and placed subcutaneously behind the neck. Twenty four-48 hours after cannulation, a chronic constriction injury (CCI) surgery was performed on the contralateral sciatic nerve. Hyperalgesia and allodynia symptoms were assessed 2, 4, 6, 8, 10 and 12 days after CCI. Microinfusion of TNFα (100ng/day) into the LC significantly exacerbated the hyperalgesia in rat models of neuropathic pain on days 2 and 8 after CCI. On the other hand, microinfusion of TNFα antibody (250ng/day) decreased the symptoms of hyperalgesia on days 2, 4, 6, 8, 10 and 14. TNFα antibody also significantly alleviated the CCIinduced allodynia. These data suggest that alterations of TNFα levels in the LC play a crucial role in the development and maintenance of neuropathic pain.

This study was aimed to investigate the effects of postconditioning by natural honey on cardiac arrhythmias in the ischemic isolated rat heart. Male Wistar rats were divided into four groups then anesthetized by sodium pentobarbital. The animal hearts were removed and quickly mounted on a Langendorff apparatus and perfused under constant pressure by a modified Krebs-Henseleit (K/H) solution that was previously equilibrated with 95% O2–5% CO2. The hearts were subjected to 30 min regional ischemia followed by 30 min reperfusion. In the control group, the hearts perfused by normal K/H solution, however in the postconditioning groups, they were perfused with natural honey (0.25, 0.5 and 1%) enriched K/H solution from 10 min before to 10 min after reperfusion. The ECGs were analyzed to determine the total number of ventricular ectopic beats (VEBs), ventricular tachycardia (VT), the incidence and duration of VT and ventricular fibrillation (VF) during last 10 min of ischemia and the first 30 min of reperfusion. During ischemia, honey (0.25, 0.5 and 1%) produced significant reduction in the number of VEBs and number, duration and incidence of VT (P<0.01). The incidence and time spent in VF were lowered by honey compared to the control group (P<0.05). During reperfusion time, all used concentrations of honey significantly reduced the number of VEBs (P<0.05). In addition, honey (0.5 and 1%) decreased the number and duration of VT (P<0.01 and P<0.05, respectively). Moreover, VF duration was lowered by perfusion of honey (0.25 and 0.5 %) versus the control group (P<0.05). The results showed protective effects of postconditioning by honey against ischemia-reperfusion injuries as anti-arrhythmic activities. Probably, antioxidant activity of honey, by scavenging of free radicals, and the presence of important energy sources such as glucose and fructose by improvement of cardiac function may involve in these protective effects.

Estrogen is one of the gonadal hormones that has multiple beneficial actions in central nervous system and involves in learning and memory. Alzheimer's disease (AD) is a progressive neurodegenerative disorder that impairs patient memory. The human nucleus basalis of Meynert (nBM) is severely affected in Alzheimer's disease. So in this study the effect of peripheral (intramuscular) injection of estradiol banzoate on passive avoidance memory was investigated in adult male wistar rats. nBM bilateral electrical lesion rats were divided in to control, lesion, sham (lesion+ 0.2ml sesame oil) and estradiol treatment (lesion+ 0.2, 0.4, 0.8, 1.2 mg/kg). After injection estradiol or sesame oil (vehicle) each rat was trained by shuttle box one week. In this study two factors, latency in entering dark chamber and time spending in the dark chamber was considered. Statistical analysis showed that nBM bilateral lesion decrease the passive avoidance memory (P<0.01). Injection 0.2mg/kg estradiol does not improve memory. While injection 0.4 and 0.8mg/kg estradiol have improved memory (p<0.05, p<0.01). But injection 1.2 mg/kg estradiol does not have distinctive effect on passive avoidance memory. Estradiol benzoate affects passive avoidance memory in a dose dependent manner. It seems that estrogen improve memory through an interaction with cholinergic system via genomic and non-genomic mechanisms.

There is no comprehensive study on the effect of Folate on food intake; therefore the present study was carried out to determine the effect of Folate supplementation on serum concentrations of Leptin and Grehlin and food intake in male Wistar rats. The study was carried out for 42 days during which the animals were weighed weekly; their food and water intakes were measured every 48 hours. Serum leptin, ghrelin and insulin were measured using ELISA. Repeated Measures and t-test were done to analyze the data. The amount of water intake in the case group was significantly (p<0.05) higher that the control group, food intake was also higher in the group receiving folate as compared to the control although it did not reach the significance level. The Body weight of the rats receiving the supplement were significantly (p<0.001) higher than the control group. The experimental group had higher serum leptin and lower serum ghrelin levels although not significantly. Serum insulin level was significantly higher in the experimental group (p<0.001). A significant correlation was found between Water and food intake (r=0.9, p<0.001), and between body weight and the food intake (r=0.6, p<0.001). There was a significant correlation between serum insulin level with food intake (r=0.6, p< 0.001) and body weight (r=0.36, p=0.05). Daily folate supplementation for a long period increased body growth and food intake in weaning rats. Since serum ghrelin level was also higher, it is possible that increased weight was related to the other body tissues, rather than adipose tissue.

Drugs of abuse such as nicotine and morphine used systemically by addicts produce their effects via the mesolimbic dopaminergic pathway. Furthermore, evidence indicates that some behavioral effects of nicotine and morphine are mediated by nitric oxide (NO). Based on these observations, the aim of the present study was to investigate the effects of intra-nucleus accumbens (NAc) injection of a nitric oxide synthase (NOS) inhibitor, L-NAME, on the nicotine’s effect on the morphine-induced amnesia. As a model of memory assessment, a step-through type passive avoidance task was used. All animals were bilaterally implanted with a chronic cannulae in the NAc shell and trained by using a 1 mA foot shock. Animals were tested 24 h after training to measure step-through latency. Post-training injection of morphine impaired memory performance on the test day. Pre-test administration of the same doses of morphine reversed amnesia induced by post-training administration of morphine. Moreover, administration of nicotine before the test prevented morphine amnesia. Impairment of memory because of post-training injection of morphine was also prevented by pretest administration of L-NAME. Co-administration of an ineffective dose of nicotine with ineffective doses of L-NAME synergistically improved memory that was impaired by morphine. On the other hand, pre-test intra-NAc injection of L-NAME impaired passive avoidance memory by itself. Considering the effects of pre-test intra-NAc injection of L-NAME alone or in combination with ineffective dose of nicotine on morphine amnesia, it may be concluded that nitric oxide system of nucleus accumbens has an important role in the improvement of morphine-induced amnesia and morphine state-dependent memory caused by nicotine.

This research was aimed at examining acute responses of hormones such as growth hormone (GH), total testosterone (TT), free testosterone (FT), free fatty acid (FFA) and cortisol to resistance (R), endurance (E) and endurance-resistance (ER) exercise.

The participants of this study were 10 healthy young men. R protocol included bench press, lateral pull down, leg extension and leg curl. E protocol comprised of 30 minutes pedaling by cycle ergometer at 70% maximum heart rate. In the ER protocol, the participants first went through the E protocol and after an interval of 15 minutes they performed the R protocol. In the control group they did not do any exercise. Blood samples were collected before, immediately after and 15 minutes after exercise.

Results indicated that GH and FT were significantly increased after all 3 protocols (P<0.05). TT and FFA were significantly increased after R and E protocols, respectively (P<0.05). Comparison between groups indicated a significant difference between GH and FT. Cortisol was significantly decreased in the E and ER protocols and the control group (P<0.05) but it did not have a significant decrease in the R protocol.

The E and ER protocols can increase GH with lower lactate and cortisol production, while the R protocol provides better anabolic environment for development and hypertrophy of muscle fiber because of higher stress, metabolic and hormonal responses. The increase of FFA after the E protocol was probably the cause of reduction of GH and TT secretion in the ER protocol.