Fibroblast Growth Factor-2 Enhanced The Recruitment of Progenitor Cells and Myelin Repair in Experimental Demyelination of Rat Hippocampal Formations

Objective: Hippocampal insults have been observed in multiple sclerosis (MS) patients. Fibroblast growth factor-2 (FGF2) induces neurogenesis in the hippocampus and enhances the proliferation, migration and differentiation of oligodendrocyte progenitor cells (OPCs). In the current study, we have investigated the effect of FGF2 on the processes of gliotoxin induced demyelination and subsequent remyelination in the hippocampus. Materials and Methods: In this experimental study adult male Sprague-Dawley rats received either saline or lysolecithin (LPC) injections to the right hippocampi. Animals received intraperitoneal (i.p.) injections of FGF2 (5 ng/g) on days 0, 5, 12 and 26 post-LPC. Expressions of myelin basic protein (Mbp) as a marker of myelination, Olig2 as a marker of OPC proliferation, Nestin as a marker of neural progenitor cells, and glial fibrillary acidic protein (Gfap) as a marker of reactive astrocytes were investigated in the right hippocampi by reverse transcriptase-polymerase chain reaction (RT-PCR). Results: There was reduced Mbp expression at seven days after LPC injection, increased expressions of Olig2 and Nestin, and the level of Gfap did not change. FGF2 treatment reversed the expression level of Mbp to the control, significantly enhanced the levels of Olig2 and Nestin, but did not change the level of Gfap. At day-28 post- LPC, the expression level of Mbp was higher than the control in LPC-treated animals that received FGF2. The levels of Olig2, Nestin and Gfap were at the control level in the non-treated LPC group but significantly higher in the FGF2-t reated LPC group. Conclusion: FGF2 enhanced hippocampal myelination and potentiated the recruitment of OPCs and neural stem cells (NSCs) to the lesion area. Long-term application of FGF2 might also enhance astrogliosis in the lesion site

Low-frequency Stimulation Decreases Hyperexcitability Through Adenosine A1 Receptors in the Hippocampus of Kindled Rats

Introduction: In this study, the role of A1 adenosine receptors in improving the effect of Low-Frequency Electrical Stimulation (LFS) on seizure-induced hyperexcitability of hippocampal CA1 pyramidal neurons was investigated. Methods: A semi-rapid hippocampal kindling model was used to induce seizures in male Wistar rats. Examination of the electrophysiological properties of CA1 pyramidal neurons of the hippocampus using whole-cell patch-clamp recording 48 h after the last kindling stimulation revealed that the application of LFS as two packages of stimulations at a time interval of 6 h for two consecutive days could significantly restore the excitability CA1 pyramidal neurons evidenced by a decreased in the of the number of evoked action potentials and enhancement of amplitude, maximum rise slope and decay slope of the first evoked action potential, rheobase, utilization time, adaptation index, first-spike latency, and post-AHP amplitude. Selective locked of A1 receptors by the administration of 8-Cyclopentyl-1,3-dimethylxanthine (1 μM, 1 μl, i.c.v.) before applying each LFS package, significantly reduced LFS effectiveness in recovering these parameters.  Results: On the other hand, selective activation of A1 receptors by an injection of N6-cyclohexyladenosine (10 μM, 1 μl, i.c.v.), instead of LFS application, could imitate LFS function in improving these parameters.  Conclusion: It is suggested that LFS exerts its efficacy on reducing the neuronal excitability, partially by activating the adenosine system and activating its A1 receptors

Inhibitory effect of orexin-A on GABAergic synaptic transmission in rat locus coeruleus neurons

Background: The locus coeruleus (LC) contains large clusters of noradrenergic neurons which project widely throughout the central nervous system including hypothalamus. The LC is involved in cognitive processes, including attention, learning, memory and drug addiction. Orexin neuropeptides excite the noradrenergic LC neurons; however, its effects on inhibitory synaptic transmission to the LC neurons are unknown. Materials and Methods: Here, we investigated the effect of orexin-A (100 nM) on sIPSCs in LC neurons. We used whole-cell patch clamp recording in rat horizontal slices containing the LC nucleus. Results: Our electrophysiological data indicate that orexin-A application only decreased sIPSCs frequency of LC neurons that was blocked by SB-334867, selective orexin type-1 receptors. Conclusion: In this study, our findings suggest that orexin-A depresses sIPSCs frequency through orexin type-1 receptors. It can be deduced that these changes in inhibitory synaptic transmission may be elicited by prestsynaptic mechanism. These results provide in vitro evidence for a critical role of orexin signaling in LC neurons. Â

Investigating the Effects of Low Frequency rTMS on Kindled Seizure in Rats

Introduction: Neural stimulation is a promising new technology for the treatment of medically-intractable seizures.  Transcranial Magnetic Stimulation (TMS) is a simple, non-invasive, low cost technique which is widely used in neurophysiology. In a few studies that have been performed at different frequencies the therapeutic effects of this technique were not obvious. Repetition of low frequencies TMS (≤1 Hz) has inhibitory and quenching effects on neuron activities and it decreases the excitability of the cortex. In epilepsy, as a disease of the central nervous system, the excitability of the cortex increases. It seems that such a technique at its optimum frequencies has therapeutic potential in epilepsy. Materials and Methods: In this study, the effect of 0.1, 0.5, 1 and 2 Hz repetitive Transcranial Magnetic Stimulation (rTMS) at an  intensity of  80% Resting Motor Threshold (RMT) and at 1 Hz with an  intensity of  90 and 100% RMT  on Amygdala-kindling model in rats in optimum spatial coordinate was investigated. The procedure includes delivering a daily 5 minute rTMS stimulus using a butterfly figure coil having 25 mm in diameter and the coordinate which induces the maximum electrical field in Amygdala area.  The stimulus was given within five minutes after the electrical kindling stimulus was delivered.  The number of days to reach stage 1, 2, 3, 4 and 5 of kindling model After Discharge Duration (ADD) in each day and the percentage of cumulative ADD between the treated and the control group was statistically compared.  Two groups were used to investigate the effect of the intensity of the magnetic field. A frequency of 1 Hz rTMS at an intensity of 90% and 100% RMT was delivered with the same physical parameters as before. Results: Using a frequency of 1 Hz rTMS at an intensity of 80% and RMT of 90% showed a significant inhibitory effect on the spread of seizure into other areas of brain in comparison to the control group. Increasing the intensity of the magnetic field from 80 to 90% RMT increased the inhibitory effect of this technique.  However, the quenching effect was significantly decreased when the intensity of the magnetic field was increased to 100% RMT. Discussion and Conclusion:  It seems that the frequency of rTMS and Motor Threshold of subject are important factors in causing physiological effects. This study showed that rTMS technique at some frequencies and intensities may have therapeutic effect on epilepsy

The Effects of Bone Marrow Stromal Cells Therapy on the Improvement of Epilepsy Model in Rat Induced by pilocarpine

Objective: Temporal lobe epilepsy is the most common type of epilepsy in adult humans, which is characterized clinically by a progressive development of spontaneous recurrent seizures of temporal lobe origin. Because of the side effects of current treatment protocols, the resistance to pharmacological therapy in this investigation, bone marrow stromal cells were used to evaluate the recovery of epileptic rats induced by pilocarpine. Materials & Methods: In this randomized experimental research, the rats were divided into five groups, controls (untreated), three treated groups (12, 24 and 36 hours) and a group treated with the vehicle only. The animals in chronic phase were monitored via video monitoring system for three weeks (day & night). For assessment of the response for the treatment of epileptic’s rat using BMSCs therapy, Racine scale was used as a behavioral test. BMSCs (2 – 3 million cells) were labeled with BrdU and were injected via tail vein rat 12, 24, 36 hours after first seizure. After 6 week all rats sacrificed and processed for paraffin, sectioned and for Cresyl violet staining. Data were analyzed by use of Wilcoxon signed Ranks test and Tukey’s test. Results: The result of the study showed that the behavioral test in three week as follows: in control group (untreated), number of seizure is 6.25±1.3 in vehicle group, number of seizure was 6.2±0.8 the group which received BMSCs 12 h after seizure all rats died the group which received BMSCs (24 h after seizure), the number was 2±0.4 and the group which received BMSCs (36 h after seizure), the number of seizure was 2.25±0.47. There was significant difference between treated (2 and 36 hours) groups and other groups in number of seizure (P<0/01). Also, cells number was different significantly between same groups (P<0/01). Conclusion: Intravenous injection of BMSCs can improve number of attacks in epileptic’s rats. Also, BMSCs injection can prevent from decrease of cells numerical density and degenerative damage

Parvalbumin-expressing interneurons can act solo while somatostatin-expressing interneurons act in chorus in most cases on cortical pyramidal cells

Neural circuits in the cerebral cortex consist primarily of excitatory pyramidal (Pyr) cells and inhibitory interneurons. Interneurons are divided into several subtypes, in which the two major groups are those expressing parvalbumin (PV) or somatostatin (SOM). These subtypes of interneurons are reported to play distinct roles in tuning and/or gain of visual response of pyramidal cells in the visual cortex. It remains unclear whether there is any quantitative and functional difference between the PV → Pyr and SOM → Pyr connections. We compared unitary inhibitory postsynaptic currents (uIPSCs) evoked by electrophysiological activation of single presynaptic interneurons with population IPSCs evoked by photo-activation of a mass of interneurons in vivo and in vitro in transgenic mice in which PV or SOM neurons expressed channelrhodopsin-2, and found that at least about 14 PV neurons made strong connections with a postsynaptic Pyr cell while a much larger number of SOM neurons made weak connections. Activation or suppression of single PV neurons modified visual responses of postsynaptic Pyr cells in 6 of 7 pairs whereas that of single SOM neurons showed no significant modification in 8 of 11 pairs, suggesting that PV neurons can act solo whereas most of SOM neurons may act in chorus on Pyr cells

Low Frequency Stimulation Reverses the Kindling-Induced Impairment of Learning and Memory in the Rat Passive-avoidance Test

Introduction: The life quality of patients with epileptic seizures is highly affected by cognitive deficits. Low Frequency Stimulation (LFS) is a novel approach for the treatment of pharmacoresistant epilepsy. The main goal of this research is investigating the possible effect of LFS on seizure-induced cognitive dysfunction. Methods: To this end, the kindled animal were prepared via CA1 electrical stimulation in a semi-rapid way (12 stimulations/day). A group of animals were stimulated with LFS, 4 times at 30 s, 6 h, 24 h, and 30 h after the last kindling stimulation. Applied LFS was administered in 4 packages every 5 minutes. The packages were designed with 200 monophasic 200 monophasic square wave pulses of 0.1 ms duration at 1 Hz. The passive-avoidance test was conducted on all animals in order to measure the learning and memory behavior. Results: Hippocampal kindled rats showed deficits in learning and memory when passive avoidance test was performed. Application of LFS reversed the impairment in learning and memory behavior in kindled rats. At the same time, LFS markedly diminished kindling-induced neuronal loss and atrophy in the hippocampus. Conclusion: LFS may have some protection against seizure-induced cognitive damage in kindled rats