Effect of ramosetron, a 5-HT3 receptor antagonist on the severity of seizures and memory impairment in electrical amygdala kindled rats

The entorhinal cortex (EC) plays a pivotal role in epileptogenesis and seizures. EC expresses high density of serotonergic receptors, especially 5-HT3 receptors. Cognitive impairment is common among people with epilepsy. The present study investigated the role of 5-HT3 receptor on the severity of seizures and learning and memory impairment by electrical kindling of amygdala in rats. The amygdala kindling was conducted in a chronic kindling manner in male Wistar rats. In fully kindled animals, ramosetron (as a potent and selective 5-HT3 receptor antagonist) was microinjected unilaterally (ad doses of 1, 10 or 100 µg/0.5 µl) into the EC 5 min before the novel object recognition (NOR) and Y-maze tests or kindling stimulations. Applying ramosetron at the concentration of 100 μg/0.5 µl (but not at 1 and 10 µg/0.5 µl) reduced afterdischarge (AD) duration and increased stage 4 latency in the kindled rats. Moreover, the obtained data from the NOR test showed that treatment by ramosetron (10 and 100 µg/0.5 µl) increased the discrimination index in the fully kindled animals. Microinjection of ramosetron (10 and 100 µg/0.5 µl) in fully kindled animals reversed the kindling induced changes in the percentage of spontaneous alternation in Y-maze task. The findings demonstrated an anticonvulsant role for a selective 5-HT3 receptor antagonist microinjected into the EC, therefore, suggesting an excitatory role for the EC 5-HT3 receptors in the amygdala kindling model of epilepsy. This anticonvulsive effect was accompanied with a restoring effect on cognitive behavior in NOR and Y-maze tests.

Apoptosis in the Dentate Nucleus Following Kindling-induced Seizures in Rats

Background: Epilepsy is a common neurological disorder characterized by abnormal and recurrent neuronal discharges that result in epileptic seizures. The dentate nuclei of the cerebellum receive excitatory input from different brain regions. Purkinje cell loss due to chronic seizures could lead to decreased inhibition of these excitatory neurons, resulting in the activation of apoptotic cascades in the dentate nucleus. Objective: The present study was designed to determine whether there is a presence of apoptosis (either intrinsic or extrinsic) in the dentate nucleus, the final relay of the cerebellar circuit, following kindling-induced seizures. Methods: In order to determine this, seizures were triggered via the amygdaloid kindling model. Following 0, 15, or 45 stimuli, rats were sacrificed, and the cerebellum was extracted. It was posteriorly prepared for the immunohistochemical analysis with cell death biomarkers: TUNEL, Bcl-2, truncated Bid (tBid), Bax, cytochrome C, and cleaved caspase 3 (active form). Our findings reproduce results obtained in other parts of the cerebellum. Results: We found a decrease of Bcl-2 expression, an anti-apoptotic protein, in the dentate nucleus of kindled rats. We also determined the presence of TUNEL-positive neurons, which confirms the presence of apoptosis in the dentate nucleus. We observed the expression of tBid, Bax, as well as cytochrome C and cleaved caspase-3, the main executor caspase of apoptosis. Conclusion: There is a clear activation of both the intrinsic and extrinsic apoptotic pathways in the cells of the dentate nucleus of the cerebellum of rats subjected to amygdaloid kindling.

Neuroprotective Effect of Celastrus Paniculatus Seed Extract in Epilepsy and Epilepsy-Associated Cognitive Deficits

Purpose: Cognitive deficit is one of the common comorbidity accompanying epilepsy. The present study evaluated the effect of Celastrus paniculatus (C- paniculatus) seed extract on seizure severity and cognitive deficit following Pentylenetetrazole (PTZ) -induced chemical kindling model. Methods : PTZ kindling model was developed by daily administration of sub-convulsive dose of PTZ 30 mg/kg for 4 weeks. After 4 weeks of induction, the following treatment namely Sodium valproic acid (SVA) 200 mg/kg, C- paniculatus 500 mgkg, Pergolide 2 mg/kg alone and combination groups C- paniculatus 250 mgkg+ Pergolide 1 mg/kg and C- paniculatus 250 mgkg+ SVA 100 mg/kg were administered 30 minute prior to PTZ 30 mg/kg injection for a period of next 14 days. Neurobehavioral parameters Morris water maze test (MWM), Grip strength test (GPS) brain superoxide dismutase (SOD), Catalase, reduced glutathione (GSH) and dopamine level. Hematoxylin & Eosin (H&E) staining of hippocampus pyramidal layers Cornu ammonis (CA1), CA2, CA3, dentate gyrus (DG), and frontal cortex were assessed. Results: C- paniculatus 500 mg/kg alone and combination groups C- paniculatus 250 mgkg+ Pergolide 1 mg/kg and Celastrus paniculatus 250 mgkg+ SVA 100 mg/kg significantly (p<0.05) reduced the seizure score, mean latency time, and distance traveled in MWM. However, no significant effect was seen in grip strength test. Biochemical analysis showed elevated antioxidant markers namely GSH, catalase, and SOD & elevated dopamine levels. C- paniculatus and its combination were also found significantly (p<0.05) protected against neuronal loss in hippocampus and frontal cortex as evidenced by H&E staining. Conclusion: C- paniculatus alone and its combination may have the potential to treat epilepsy and associated cognitive deficits.

Anticonvulsive and anti-epileptogenesis effects of Echinacea purpurea root extract, an involvement of CB2 receptor

Objective Phytocannabinoids beyond the Δ9-tetrahy-drocannabinol have shown anticonvulsive effects. Also, alkylamides from Echinacea purpurea have been proved as cannabinomimetics. We examined the effect of the hydroalcoholic root extract of E. purpurea on pentylenetetrazol (PTZ)-induced tonic–clonic seizures and kindling model of epileptogenesis and the involvement of CB2 receptors as the mediator of this effect. Methods Male Wistar rats (200 ± 20 g) were used. Single intraperitoneal (i.p.) injection of PTZ (80 mg/kg) was used to induce tonic–clonic seizures. The kindling model of epileptogenesis was induced by daily injections of PTZ (37 mg/kg; i.p. for 15 days). Latency and duration of the stages were monitored for analysis. The hydroalcoholic root extract of E. purpurea was injected (i.p.) 20 min before seizure induction at the doses of 10, 50, 100 and 200 mg/kg. CB2 receptor antagonist SR144528 was injected (0.1 mg/kg; i.p.) 20 min before the Echinacea injection. Results In the tonic–clonic model, pretreatment with E. purpurea at the doses of 100 and 200 mg/kg significantly increased latencies to S2–S6, while it significantly decreased S6 duration and mortality rate. SR144528 injection before the injection of 100 mg/kg of E. purpurea significantly prevented the effects of the extract on S4–S6 latencies. In the kindling model, E. purpurea at the doses of 100 and 200 mg/kg significantly delayed epileptogenesis and decreased mortality rate, while SR144528 injection before the injection of 100 mg/kg of E. purpurea significantly blocked this effect of the extract. Conclusion These findings revealed the anticonvulsive and antiepileptogenesis effects of the E. purpurea root extract, which can be mediated by CB2 receptors.