Physiology and Pharmacology
Year:2011 | Volume:15 | Issue:1|Papers Count:25

Introduction: A close link between spreading depression (SD) and several neurological diseases such as epilepsy could be demonstrated in many experimental studies. Epilepsy is among the most common brain disorders. Despite a large number of investigations, its mechanisms have not been yet well elucidated. Hippocampus is one of the important structures involved in seizures. The aim of this study is to get an insight into the patho-physiological processes induced by SD that lead to the generation of epileptiform field potentials.Methods: The horizontal amygdala-hippocampus-neocortex slices of rat brain in which SD was induced by KCl application in each brain structure were used. Following GABAA receptor antagonist bicuculline superfusion (1.25mmol/L, for 45 min), SD induced epileptic activity in all tested slices was monitored.Results: The induction of SD in the hippocampus resulted in interictal and ictal epileptiform field potentials and intracellular paroxysmal depolarization shifts (PDS). After SD, RMP slightly depolarized and the threshold of AP decreased, while the frequency of AP significantly increased. Amplitude of depolarization and also amplitude of discharges were also significantly increased. ISI significantly decreased and the most of neurons shifted from FA to SA indicating an enhanced excitability.Conclusion: SD may cause pathological changes in brain structures such as increased excitation and/or decreased inhibition. Propagation of SD over epileptogenic areas may trigger seizure attacks in some patients and our findings provide evidence on the role of SD in temporal lobe epilepsy.

Introduction: we have recently reported the presence of two potassium currents with 598 and 368 pS conductance in the rough endoplasmic reticulum(RER) membrane. The 598 pS channel was voltage dependent and ATP sensitive.However, the 368 pS channel was rarely observed and its identity remained obscure. Since cationic channels in intracellular organelles such as mitochondria and RER play important roles in intracellular signaling and cellular protection, studying their biophysical and pharmacological properties is important.Methods: we used channel incorporation into bilayer lipid membrane method. L-a-Phosphatidylcholine (PC), a membrane lipid, was extracted from fresh egg yolk. Bilayer lipid membrane was formed in a 150 mm diameter hole.Rough endoplasmic reticulum vesicles were obtained from liver after homogenization and several centrifugations. All recordings were filtered at 1 kHz and stored at a sampling rate of 10 kHz for offline analysis by PClamp9. Statistical analysis was performed based on Markov noise free single channel analysis.Results: A 364 pS potassium channel was identified which was voltage independent in+50 to -50 mV voltages. In all voltages, open probability (Po) was over 0.9. Nonspecific inhibitor of K+channels, 4-aminopyridine (4-AP, 20 mM), inhibited the channel activity. However, intracellular nucleotide like ATP had no effect on channel gating.Conclusion: We observed a new potassium channel with 346 pS conductance in RER membrane that unlike the 598 pS K channel was not ATP sensitive. This channel may play an important role in Ca2+ homeostasis and cell protection.

Introduction: Anethole is the main constituent of Pimpinella anisum L. (anise), a herbaceous annual plant which has several therapeutic effects. In the folk medicine, anise is employed as an antiepileptic drug. Specifically, this study was focused on the cellular effect of anethole, an aromatic compound in essential oils from anise and camphor.Anethole has various physiological effects on the cardiovascular system and smooth and skeletal muscles. However, despite these persistent effects, there is little information available about the actions of anethole on nerve cells.Therefore, a major goal of the present research was to investigate the possible cellular mechanisms underlying the effect of anethole on the neural excitability and action potential characteristics in snail neurons.Methods: Intracellular recordings were made under the current clamp condition on F1 cells of Helix aspersa.Following extracellular application of anethole (0.5% or 2%), changes in thefiring pattern and action potential parameters were assessed and compared to control condition.Results: Application of anethole (0.5% and 2%) led to a significant increase in the action potential amplitude and a reduction in the peak area and time to peak. In the presence of 0.5% anethole, the after hyperpolarization (AHP) amplitude was significantly decreased, while the firing frequency of neurons was increased. However, 2% anethole did not affect the AHP amplitude, but significantly reduced the firing frequency of action potentials.Conclusion: Based on the effect of anethole on the action potential parameters, it can be concluded that it probably affects the voltage gated ion channels function, including Ca2+channels and/or Ca2+dependent K+channels activity.

Introduction: Despite extensive studies that have been performed on the effects of Crataegus monogyna in cardiovascular diseases, only few investigations have addressed the antiarrhythmic properties of this plant. Aims of the present study were: 1) To determine the protective role of methanolic extract ofC. monogyna on the rate-dependent model and the concealed conduction of the AV node.2) To explore the role of Na+-K+ATPase in the protective role of C. monogyna Methods: Male New Zealand rabbits (1.5-2kg) were used in all experiments. Stimulation protocols were used to measure basic and rate-dependent AV nodal properties (recovery, atrial fibrilation and zone of concealment) in two groups (N=14). In the first group, all the stimulation protocols were performed before and after the administration of different concentrations ofC. monogyna extract (n=7), while in the second group (n=7), all stimulation protocols were carried out in the presence of ouabaine (0.05mM) and the plant extract.Results: Basic and rate-dependent properties of the AV node were inhibited after the addition of the extract of C.monogynato Kerebs Henselite solution. At the maximum concentration of C. monogyna (30 mg/l), WBCL cycle length was significantly increased from 156.5±3.4 to 173±5.8 ms and the nodal functional refractory period was prolonged from 164.4±4.1 to 182.7±3.8 ms (P <0.05). Significant decreases of ventricular rhythm were recorded in both selective concentrations of the plant extract. The depressant electrophysiological effect ofC. monogyna on the AV node was not abolished by ouabaine, a selective inhibitor of Na+-K+ATPase enzyme.Conclusion: The results showed a potential anti-arrhythmic and protective effect for C. monogyna. The effect of the plant extract in increasing nodal refractory period and widening of the concealment zone might be the major mechanisms involved. The protective role of C. monogyna was not related to the Na+-K+ATPase activity.

Introduction: Previous studies have shown that stimulation of lateral hypothalamus (LH) produces antinociception.Orexin-A (OXA) receptor is strongly expressed in the nucleus locus coeruleus (LC) and orexinergic fibers densely project from LH to LC. In this study, we assessed the role of LC and its OXA receptors in antinociceptive response induced by LH chemical stimulation in the rat.Methods: The cholinergic agonist carbachol (125nmol/0.5ml saline) and lidocaine (2%; 0.5ml) were unilaterally microinjected into the LH with the concurrent LC inactivation. In another set of experiments, SB-334867 an OXA selective antagonist or its vehicle were unilaterally infused in LC to study its effect on LH stimulation-induced antinociception. Antinociceptive responses were obtained by the tail flick test and were presented as maximal possible effect (MPE) at 5, 10, 15, 20, 30 and 60 min after drug administrations.Results: The results showed that microinjection of carbachol into the LH significantly induced antinociception at 5 and 10 min (p<0.001). This effect was significantly blocked by microinjection of lidocaine into the LC. Additionally, intra-LC administration of SB-334867 (4.5 mg) could suppress the LH stimulation-induced antinociception by carbachol at 5 and 10 min post-injection times (p<0.001).Conclusion: Our findings showed that analgesic response induced by LH stimulation is mediated in part by the subsequent activation of LC neurons and results from the activation of orexinergic inputs into the LC that can modulate the pain processing.

Introduction: Oral delivery is the most favorable route for insulin administration. The aim of this study was to generate new chitosan coated insulin nanoliposomes and then to assess the physiological efficacy of these nanoliposomes after oral administration in diabetic rabbits.Methods: Nanoliposomes with negative surface charge encapsulating insulin were prepared by reverse phase evaporation method. To prepare nanoliposomes, lecithin, cholesterol, acetyl-diphosphate and b-cyclodexterin were used. Then, nanoliposomes were coated by means of incubation with the chitosan solution. The encapsulation efficiency of prepared nanoliposomes was measured by spectrophotometry technique after dissolution of the nanoparticles. The hypoglycemic efficacy of chitosan-coated insulin nanoliposomes were investigated by monitoring the blood glucose level after oral administration to diabetic rabbits.Results: Insulin entrapment efficacy for preparation of new formulated nanoliposomes 79±0.16 were significantly higher than other formulations (p<0.05). Thein vivo results clearly indicated that the insulin-loaded nanoliposomes could effectively reduce the blood glucose level in diabetic rabbits from 250±0.75 mg/dl to 125±0.98 mg/dl after 4 hours.Conclusion: The results clearly suggest that nanoliposomes may be considered as a good tool for oral insulin delivery.

Introduction: Jugulans regia (Jugulandaceae), Astragaus hamosus (Papilionaceae), Crocus pallasii subsp.haussknechtiiboiss. (Iridaceae) and Cassia angustifolia Vahl. (Caesalpinaceae) have been suggested as antiepileptic remedies in traditional medicine of Iran. The possible anticonvulsant effect of the hydroalcoholic extract of the leaves ofJ. regia, fruits of A. hamosus, corm of C. haussknechtii, and aerial parts of C. angustifolia was evaluated in common experimental seizure tests in mice.Methods: The hydroalcoholic extracts of the plants were obtained by percolation of 100g of air-dried part of each plant in 900 ml ethanol 80%. Different doses of the extracts were intraperitoneally (i.p.) administered in mice (10 male mice in each group) and occurrence of clonic seizures induced by pentylenetetrazol (PTZ; 60mg/kg, i.p.) or tonic seizures induced by maximal electroshock (MES; 50mA, 50Hz, 0.5sec) was observed 30 min thereafter. Acute toxicity of the extracts was also assessed.Results: J. regia, C. haussknechtii, C. angustifolia did not show any anticonvulsant activity up to the maximum safe doses of 3 g/kg, 0.25 g/kg and 2 g/kg, respectively.A. hamosus had anticonvulsant effect in PTZ test at the high and sedative dose of 6 g/kg. The extracts did not affect tonic seizures induced by MES.Conclusion: J. regia, C. haussknechtii, C. angustifolia and A. hamosus had no anticonvulsant activity in PTZ and MES seizure tests.

Metabotropic glutamate receptors (mGluRs) consist of a large family of G-protein coupled receptors that are critical for regulating normal neuronal function in the central nervous system. The wide distribution and diverse physiological roles of various mGluR subtypes make them highly attractive targets for the treatment of a number of neurological and psychiatric disorders. The discovery of subtype selective ligands for these receptors has provided the tools to support a number of preclinical studies, suggesting the numerous therapeutic potential that lies in the ability selectively to modulate a specific mGluR subtype. mGluRs do not activate ion channels directly but instead through G-protiens activate second messenger mechanisms in the neurons. So far 8 subtypes of mGluRs have been identified which divided into three groups (Group I, II, and III) according to their sequence similarities, Signal transduction mechanisms and pharmacological properties. Depending on the receptor subtype, they might be localized at presynaptic or postsynaptic sites which regulate glutamate and other neurotransmitters release.As I applied many mGluR ligands on hippocampal slices and observed interesting results on synaptic transmission and modulation of certain neurotransmitters such as adenosine, I intended to study their application in neurological diseases. The method was based on my experiences from researches and different seminars to evaluate last decade development on mGluRs and their ligands application in certain neurological disorders. Therefore, aim of this review article is to describe mGluRs and their role in the excitotoxicity and neuroprotection. Then, application of different mGluR ligands for the treatment of a variety of neurological disorders including schizophrenia, Parkinson's disease, anxiety disorders, epilepsy, and drug abuse has been described.

Introduction: Gonadotropin inhibitory hormone (GnIH) has been known as a key inhibitor of the secretion of gonadotropin releasing hormone (GnRH). Ewe has estrous cycles comprising of follicular and luteal phases. Follicular phase is in turn divided into proestrous and estrous phases. Blood level of LH increases in follicular and decreases in luteal phases. The aim of the present study was to evaluate (1) the presence of GnIH neurons in the ewe preoptic area (POA) and (2) the alterations of GnIH expression during different phases of ewe estrous cycle.Methods: Three fertile three-year-old ewes in each phase (n=9) were selected and the number of GnIH neurons was estimated by using immunohistochemistry method.Results: GnIH neurons were present in the POA during different phases of estrous cycle. The number of GnIH neurons significantly increased in the luteal phase in comparison with the proestrous phase (P=0.001).Conclusion: GnIH expression in the neurons of POA of ewe is increased in the luteal phase compared to the follicular phase. This can inhibit GnRH secretion in POA and reduce LH secretion during the luteal phase.

Introduction: Recent studies have shown the presence of Cl- channels in heart and liver mitochondrial membranes.In this work, we have characterized the functional profile of a Cl- channel from rat brain mitochondria.Methods: After removing and homogenizing the rat brain, the supernatant was separately centrifuged in MSEdigitonin, H2O and Na2CO3 and mitochondrial inner membrane vesicles were obtained in MSE solution. L-a-Phosphatidylcholine (membrane lipid) was extracted from fresh egg yolk. Bilayer lipid membranes were formed in a 150 mm diameter hole. All recordings were filtered at 1 kHz and stored at a sampling rate of 10 kHz for offline analysis by PClamp10. Statistical analysis was performed based on Markov noise free single channel analysis.Results: Brain mitochondrial inner membrane preparations were subjected to SDS-PAGE analysis and channel protein reconstitution into planar lipid bilayers. Western blotting and antibodies directed against various cellular proteins revealed that the mitochondrial inner membrane fractions did not contain specific proteins of the other subcellular compartments except a very small fraction of endoplasmic reticulum. Channel incorporation into the planar lipid bilayers revealed an anion selective channel with a conductance of 301 pS in 200 mM KCl cis/50 mM KCl trans.The channel open probability appeared to be voltage dependent and the channel was active between the voltages of -40 and+20 mV. Adding 10 mM DIDS to the side corresponding to the cell internal medium caused a strong inhibition of the channel activity.Conclusion: This channel is likely to be involved in maintaining proper pH, membrane potential, ATP synthesis, and cell protection.

Introduction: Olive leaf contains anti-inflammatory and COX-2 inhibitor compounds. Considering the role of the COX enzyme in seizures, this research was performed to assess the effects of this extract in treatment of seizures induced by PTZ.Methods: In this research, male Wistar rats (200±20 g) were injected intra-cerebroventricularly with 1 ml saline or olive leaf extract (125 mg, 250 mg and 500 mg), before the intraperitoneal administration of PTZ (80 mg/kg) for induction of seizure. Then, seizure score and onset times of every stage of seizure were recorded during 20 minutes after PTZ administration. The data was analyzed by one-way analysis of variance (ANOVA) and non parametric tests.Results: Result of this research showed that the injection of 125, 250 and 500 mg of olive leaf extract had no effect on the onset time of seizure stages 1, 2 and 3 compared to the control group (P>0.05). However, they significantly decreased the onset time of seizure stages 4 and 5 compared to the control group (P<0.05). On the other hand, olive leaf extract decreased onset time of generalized (tonic-clonic) seizures, but had no effect on partial seizures. Different doses of olive leaf extract had no effect on seizure scores.Conclusion: Olive leaf extract has convulsive property and this effect is time and dose dependent.

Introduction: Inhibition of renin angiotensin system represents an important approach in the management of cardiovascular diseases. The aim of this study was to explore the effects of pretreatment with non-hypotensive dose of angiotensin converting enzyme (ACE) inhibitor, ramiprilat and angiotensin type 1 (AT1) receptor blocker, losartan on myocardial infarct size and arrhythmias in a rat model of ischemia-reperfusion injury.Methods: Seventy male Wistar rats were divided into five groups. One group received saline as control. Other groups were given 10 mg/kg/day of losartan for one (L-1W) or ten weeks (L-10W) as well as 50 mg/kg/day of ramiprilat for one (R-1W) or ten weeks (R-10W) using a feeding needle. The rats were subjected to 30 minutes occlusion and 120 minutes reperfusion of the left coronary artery. Infarct size was determined using triphenyl tetrazolium chloride staining. Ischemia-induced ventricular arrhythmias were analyzed in accordance with the Lambeth conventions.Results: Myocardial infarct size and the number of ventricular beats were significantly reduced in R-1W group, but the reduction was not significant in L-1W. After increasing the duration of pretreatment to 10 weeks in L-10W group, the infarct size, the number of ventricular beats and the episodes of ventricular tachycardia were significantly decreased.However in R-10W group the reduction of ventricular arrhythmias was not significant Conclusion: Based on the above mentioned results it could be concluded that losartan and ramiprilat, at a nonhypotensive dose, can reduce the induction of arrhythmias and infarct size following myocardial ischemia reperfusion.These drugs appear to act in a time-dependent manner. Therefore, we expected an increased cardiac effect by long-term administration of losartan. However prolonged treatment with ramiprilat reduced its protective effect.

Introduction: Exercise training increases skeletal muscle capillary density, but the molecular mechanisms of this process are not yet clear. The aim of the present study was to investigate the effect of acute long- term submaximal exercise on serum vascular endothelial growth factor (VEGF) as the main angiogenic factor, and matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), as the degrading factors of basement membrane in sedentary men.Methods: Twelve healthy sedentary men (mean age±SD=22.37±2.30 years; mean BMI±SD 23.91±2.74) were randomly selected among the volunteers. After determining VO2 max, subjects exercised on ergometer for 1 h at 70% V02 max. Two ml of blood was taken from antecubital vein immediately after exercise and 2 hours postexercise.Serum VEGF, MMP-2 and MMP-9 were measured by ELISA.Results: Serum levels of VEGF and MMP-2 decreased immediately after exercise. Two hours after exercise, the serum VEGF remained at a lower level but serum MMP-2 returned to basal level. No change was detected in the serum levels of MMP-9 immediately and 2 h after exercise.Conclusion: Acute submaximal exercise decreased the main factors involved in the development of capillary network in sedentary men. This might be due to the fact that the submaximal exercise could not provide the two main stimulating factors of angiogenesis, i.e. shear stress and hypoxia. It could also be explained by the fact that the mechanism of development of capillary network following regular exercise training is different from that following an acute exercise.

Introduction: Fennel is rich in phytoestrogens and is used for estrogen deficiency disorders. Estrogens affect anxiety through neurochemical systems such as GABA-A receptors. In this study the effects of fennel on GABA-A and estrogen receptors in anxiety were investigated.Methods: Adult female Wistar rats weighing (180±20 g) were divided into 8 groups. Groups received saline, fennel (200, 500, 750 mg/kg), tamoxifen (15 mg/kg) +fennel (500 mg/kg), picrotoxin (1 mg/kg) +fennel (500 mg/kg). A control group was also used. Elevated plus maze was used for evaluation of anxiety by measuring the time spent in the open arm. All drugs were administered intraperitoneally.Results: The results showed that fennel only at the dose of 500 mg/kg had significant anxiolytic effects and increased the time spent in open arms (P<0.01). Picrotoxin (GABA-A antagonist) significantly prevented anxiolytic effect of 500 mg/kg of fennel (P<0.001). Tamoxifen, an estrogen receptor antagonist, also abolished the anxiolytic effect of fennel (P<0.001).Conclusion: Fennel reduced anxiety in rats and picrotoxin, a non-competitive antagonist of GABA-A receptors, as well as tamoxifen, an antagonist/agonist of estrogen receptors, reduced this anxiolytic effect. Thus fennel as a herbal drug seems to have an anxiolytic effect and it probably acts through GABA-A and estrogen receptors.

Introduction: Researchers have long been interested in the effects of low intensity (less than 500 microtesla) and Extremely Low Frequency Magnetic Fields (ELF-MF, less than 300 Hz) on human’s brain activity. In this study, our purpose was to analyze the effect of local magnetic field pulses around brain regions Cz, C3, C4 on human electroencephalogram (EEG) and induction of resonance effect for medical utilization in Low Energy Neurofeedback System (LENS).Methods: EEG of 15 healthy women was recorded in four sessions (3 exposure sessions and one session as sham).In exposure sessions, ELF-MF pulses were exerted locally for 3 minutes with intensities of 100, 200 and 300 microtesla with frequencies of 10 Hz on region Cz, 18 Hz on region C3 and 14 Hz on region C4. Frequency bands power were extracted from participants' EEGs and were compared during, before and after the exposure with each other and with the sham session. Comparison between exposure groups and sham group were performed with independent t-test and paired t-test.Results: The results showed that pulsed and local ELF-MF decreases the beta band power in all three regions during the exposure (7.9 to 11.6 percent) in comparison with before the exposure with 95% certainty. Meanwhile developed variations during the exposure are transient and different from variations after interruption of exposure. The resonance effect was observed nowhere around the regions.Conclusion: Exertion of ELF-MF pulses on human brain locally change the EEG pattern and alterations persist for 15 minutes after exposure. Also EEG of other central regions varies. Therefore for recognition of effects of these fields and application of them in LENS we should consider simultaneous exposure and interhemispheric ELF-MF.