Investigation of the role of nicotinic acetylcholine receptors in modulating epileptiform activity

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that have been implicated in a variety of brain functions as well as pathological states. In the Mppocampus, nAChRs appear to modulate both excitatory and inhibitory circuits. The numerous subunits that make up nAChRs result in a great diversity of functional receptors, equipping them with different pharmacological and biophysical properties. It has recently been found that certain forms of epilepsy may arise from mutation in the genes responsible for encoding of nAChR subunits. Moreover, many reports have shown that high doses of nicotine induce seizures in animals, which are blocked by different nAChR antagonists. However, the mechanism underling the role of nAChRs in patterning epileptiform activity is poorly understood. This project aims to establish the role that nAChRs may play in experimental models of epilepsy and to assess whether pharmacological agents acting at these receptors might represent a novel avenue for developing future anticonvulsants. To assess the possible modulatory influence of nAChRs on epileptiform activity, a range of nAChR ligands were applied during experimentally induced epileptiform activity in hippocampal slices prepared from wistar rats (2-6 weeks). Extracellular recordings were obtained in the stratum pyramidale of the area CAS (n=280). Initial experiments investigated the effects of nAChR ligands on 4-aminopyridine (4AP)-induced epileptiform activity. The work presented in the rest of the thesis was focused to establish the mechanisms by which nAChRs mediate their pro-epileptogenic actions. This study demonstrates that nAChRs regulate epileptiform discharges generated by a number of different pharmacological manipulations. The cellular mechanisms generating each pattern of epileptiform activity are quite distinct involving complex interactions between synaptic and non-synaptic elements of different neuronal circuits. Since nAChRs produce a similar phenotype of modulation in each epileptiform model it is possible that nAChRs target a common cellular mechanism that is prevalent in each model and which mediates the increase in burst frequency in these models

Effect of Some Evaluation Methods on the Consequence of Final Exam for Freshman Medical Students

Background & Objective: In Iran, evaluation is one of the most important bases of medical education and one of the best criteria for the categorization of medical universities. Therefore, we aimed to compare some methods of evaluation for medical students. Methods: The target group included all basic level medical students studying medical mycology during the fifth semester. The tested methods of evaluations were: development test, post-test, class reports, and final exam. Three groups of evaluation were compared as a course plan of mycology for nine sessions. Results: There was a significant direct relation between the midterm and final exam, so that the increased midterm and post-test marks caused improvement in the final exam. Moreover, there was a relative correlation between the class reports and final exam. Conclusion: The results of the present study showed that each tested continuous evaluation is able to improve the final exams. Keywords Evaluation Medical students Final exam Midterm Post-tes

Decreased Cardiac NOX4 and SIRT-1 Protein Levels Contribute to Decreased Angiogenesis in the Heart of Diabetic Rats: Rescue Effects of IGF-1 and Exercise

Purpose: Reduced angiogenesis in the heart tissue is a primary risk factor for heart disease in the diabetes condition. This study was aimed to evaluate the changes of two main angiogenesis mediators, NADPH oxidase 4 (NOX4) and sirtuin 1 (SIRT-1) protein levels in the heart of diabetic rats and the impact of Insulin-like growth factor 1 (IGF-1) and exercise on these proteins. Methods: Injection of 60 mg/kg of streptozotocin in 40 male Wistar rats led to the induction of type 1 diabetes. Angiogenesis was detected in the hearts by immunostaining for PECAM-1/ CD31 after 30 days of treatment with IGF-1 (2 mg/kg/day) and exercise. ELISA technique was utilized to establish the expression levels of NOX4 and SIRT-1 within the heart. Results: The results revealed a significant increase in HbA1c and a significant decrease in SIRT1, NOX4 levels and angiogenesis grade in the heart of diabetes group compared to control group. Meanwhile, IGF-1 and exercise alone or in combination completely masked these effects. Additionally, synergistic effect on SIRT-1, HbA1c levels and angiogenesis grade is evident when IGF-1 and exercise are applied simultaneously. Conclusion: Our findings suggest that reduction in angiogenesis in the heart of diabetic rats may be mediated by down expression of NOX4 and SIRT-1 protein levels. It was also displayed that IGF-1 and exercise as novel therapies increase NOX4 and SIRT-1 protein levels within the hearts of diabetic rats

Prenatal Acute Stress Attenuated Epileptiform Activities in Neonate Mice

Objective: Development of the central nervous system (CNS) is dependent on interactionsbetween genetic and epigenetic factors, some of which could affect the susceptibilityof the developing brain to damaging insults. Gestational stress has been shown as a potentialfactor associated with higher risk of developing certain neurological and psychiatricdisorders. This study tested the hypothesis that maternal stress influences the risk ofepilepsy in offsprings.Materials and Methods: Pregnant mice were exposed to restraint stress twice a day forthree days at the start of the last week of gestation. Ten days after birth, the intact hippocampiof the newborn mice were excised and prepared for investigation. The hippocampiwere bathed in low magnesium artificial cerebrospinal fluid to induce field potential,and the subsequent spontaneous seizure-like events of the CA1 neurons were recorded.Plasma corticosterone was measured using a commercial radioimmunoassay (RIA) kitand the values were expressed as μg/100 ml.Results: Both the number of recurrent seizures and the duration of seizure activity werereduced in the stressed group compared to the controls (p<0.001). Stress induced a significantrise in serum corticosterone levels in both pregnant mice and in their newbornpups (p<0.001).Conclusion: These findings suggest that acute prenatal stress, which may mimic acutestress in human pregnancy, is a likely factor affecting seizure control in childhood temporallobe epilepsy. The underlying inhibitory mechanism may be an increase in the level ofneurosteroids both in the blood and the brain

Endoplasmic reticulum stress PERK-ATF4-CHOP pathway is involved in non-alcoholic fatty liver disease in type 1 diabetic rats: The rescue effect of treatment exercise and insulin-like growth factor I

Endoplasmic Reticulum Stress (ERS) is a key factor in the development of Non-Alcoholic Fatty Liver Disease (NAFLD) in diabetes. The current study aimed to examine the effects of exercise and IGF-I on ERS markers in liver tissue. Rats were divided into five groups (n = 8 per group), including control (CON), diabetes (DIA), diabetes + exercise (DIA + EX), diabetes + IGF-I (DIA + IGF-I), and diabetes + exercise + IGF-I (DIA + EX + IGF-I). Type 1 diabetes was induced by an I.P. injection of streptozotocin (60 mg/kg). After 30 days of treatment with exercise or IGF-I alone or in combination, liver tissue was assessed for caspase 12, 8, and CHOP protein levels, and expression of ERS markers (ATF-6, PERK, IRE-1A) and lipid metabolism-involved genes (FAS, FXR, SREBP-1c) by western immunoblotting. In addition, for the evaluation of histopathological changes in the liver, Hematoxylin - Eosin and Masson's Trichrome staining were done. Compared to the control group, diabetes significantly caused liver fibrosis, induced ERS, increased caspase 12 and 8 levels in the liver, and changed expression levels of genes associated with lipid metabolism, including FAS, FXR, and SREBP-1c. Treatment with either exercise or IGF-I reduced fibrosis levels suppressed ER stress markers and apoptosis, and improved expression of genes associated with lipid metabolism. In addition, simultaneous treatment with exercise and IGF-I showed a synergistic effect compared to DIA + E and DIA + IGF-I. The results suggest that IGF-1 and exercise reduced liver fibrosis possibly by reducing ERS, creating adaptive ER stress status, and improving protein folding

Effect of magnesium sulfate on hyperthermia and pentylen-tetrazol-induced seizure in developing rats

Objective(s): Febrile seizures (FS) are the most common type of convulsive events among children. Its prevalence has been estimated to be 2-5% in children between 3 months and 5 years old. Also, blood and CSF magnesium levels have been demonstrated to be reduced in children with FS. This study investigates the effect of MgSo4 pretreatment on the behaviors caused by hyperthermia (HT) and effect of these two on pentylen-tetrazol (PTZ)-induced seizure later in life. Materials and Methods: Thirty two Wistar rats were assigned to 2 groups: saline-hyperthermia-pentylentetrazol (SHP) and magnesium-hyperthermia-pentylentetrazol (MHP). In both groups, HT was induced at the age of 18-19 days old. Before the HT, MHP group received MgSo4 and SHP group received normal saline intraperitoneally (IP). Behaviors of the rats were recorded during the HT. Then, in half of each group (n=8) at the age of 25-26 days old and in other half at the age of 78-79 days, seizure was induced by PTZ. Results: The HT successfully caused convulsive behaviors in the rats and pretreatment with MgSo4 before HT attenuated HT-induced convulsive behaviors. PTZ-induced seizures a week later was more severe than those of 2 months later. Conclusion: It can be concluded that pretreatment with MgSO4 inhibits HT-induced seizure and, in a long run, this intervention reduced PTZ-induced seizure later in life

Macrophage migration inhibitory factor antagonist (p425) ameliorates kidney histopathological and functional changes in diabetic rats

Abstract Introduction: It is hypothesized that increased macrophage migration inhibitory factor (MIF) expression may contribute to diabetic nephropathy (DN) pathogenesis. The aim of the present study was to investigate the renal effects of MIF inhibition in a diabetic experimental model. Methods: Eighteen male Wistar rats (230 ± 20 g) were divided into three groups: 1) control, 2) diabetic (STZ, 50 mg/kg, dissolved in saline, ip), 3) diabetic + MIF antagonist (p425, 1 mg/kg per day, ip, on the 21th day, for 21 consecutive days). The treatment started since we founwd a significant increase in urine albumin excretion (UAE) rate in the diabetic rats in comparison with the control rats. The rats were kept individually in metabolic cages (8 AM-2 PM) and urine samples were collected in the 21 and 42th day. At the end, blood and tissue samples were collected for biochemical (BS, UPE, urine GAG, BUN, Cr, Na, and K) and histological analyses. Results: The results of this study showed that MIF antagonist (p425) significantly decreased urine protein and GAG excretion, urine protein/creatinine ratio, and serum BUN and Cr in the streptozotocin-induced DN in the rats. Pathological changes were significantly alleviated in the MIF antagonist (p425)-administered DN rats. Conclusion: Collectively, these data suggested that MIF antagonist (p425) was able to protect against functional and histopathological injury in the DN

Morphine and Naloxone Effects on Seizure in Brain Slice of Morphine-Dependent Infant Mice

Abstract Background: The aim of this study was to evaluate the effects of different concentrations of morphine and naloxone on epileptic activity in live brain slices taken from morphine-dependent and control infant mice. Materials and Methods: Forty neonatal mice were randomly selected. To establish dependency, 2, 4, 8, 16 and 32 mg / kg morphine was injected subcutaneously once daily (0.1 cc) for 5 consecutive days from day 14-18 after birth. On postnatal days 19-20, brain slices were prepared and cerebrospinal fluid was perfused with low magnesium to induce experimental- epiletform activity. The effects of 10, 100 and 1000 µM concentrations of morphine and 10 µM naloxone were investigated on epileptic activity. Chenges in the number as well as onset and amplitude of activities were considered as an indicator to determine the quantity of their effect. Results: The results showed that morphine 100 µM increased the activity while 10 and 1000 µM concentrations of morphine and 10 µM naloxone attenuated epileptic activity in both groups. Naloxone reduced pro-seizure effect of morphine, but anti-seizure effect of morphine couldn't restored by naloxone. Conclusion: Morphine has a two-phase concentration-dependent effect on epileptic activity in the infant mice; so that low and high concentrations of morphine inhibit epileptic activity, but its moderate concentration potentiates the epileptic activity. Naloxone has an anti-seizure effect

Interactive Effects of Exercise, Sex Hormones, and Transient Congenital Hypothyroidism on Long-Term Potentiation in Hippocampal Slices of Rat Offspring

Introduction: The long-term adverse effects of transient thyroid function abnormalities at birth on intellectual development are proven. The effect of exercise increases in the presence of sex hormones. The current study aimed at investigating the possibility that a combination of sex hormones and exercise has synergistic effects on neural plasticity in Transient Congenital Hypothyroidism (TCH) rats.  Methods: To induce hypothyroidism in the mothers, Propylthiouracil (PTU) was added to drinking water (100 mg/L) on the 6th day of gestation and continued until the 21st Postnatal Day. From Postnatal Day (PND) 28 to 47, the female and male pups received 17β-estradiol and testosterone, respectively. The mild treadmill exercise began 30 minutes after the sex hormones or vehicle administration. On PND 48, electrophysiological experiments were performed on brain slices.  Results: Increase of Long-Term Potentiation (LTP) was observed in sedentary-non-hormone female rats of TCH group, compared with that of the control. The exercise enhanced LTP in control rats, but the hormones showed no significant effect. The effect of exercise and sex hormone was not significant in the TCH group. The combination of exercise and testosterone enhanced LTP in TCH male rats, while the combination of exercise and estradiol or each of them individually did not produce such an effect on LTP in TCH female rats.  Conclusion: The study findings showed an increase in excitatory transmission despite the returning of thyroid hormone levels to normal range in TCH female rats. Also a combination treatment including exercise and testosterone enhanced LTP in male rats of TCH group, which was a gender-specific event