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Voltage-gated sodium channels (VGSC) have been linked to inherited forms of epilepsy. The expression and biophysical properties of VGSC in the hippocampal neuronal culture model have not been clarified. In order to evaluate mechanisms of epileptogenesis that are related to VGSC, we examined the expression and function of VGSC in the hippocampal neuronal culture model in vitro and spontaneously epileptic rats (SER) in vivo. Our data showed that the peak amplitude of transient, rapidly-inactivating Na(+) current (I(Na,T)) in model neurons was significantly increased compared with control neurons, and the activation curve was shifted to the negative potentials in model neurons in whole cell recording by patch-clamp. In addition, channel activity of persistent, non-inactivating Na(+) current (I(Na,P)) was obviously increased in the hippocampal neuronal culture model as judged by single-channel patch-clamp recording. Furthermore, VGSC subtypes Na(V)1.1, Na(V)1.2 and Na(V)1.3 were up-regulated at the protein expression level in model neurons and SER as assessed by Western blotting. Four subtypes of VGSC proteins in SER were clearly present throughout the hippocampus, including CA1, CA3 and dentate gyrus regions, and neurons expressing VGSC immunoreactivity were also detected in hippocampal neuronal culture model by immunofluorescence. These findings suggested that the up-regulation of voltage-gated sodium channels subtypes in neurons coincided with an increased sodium current in the hippocampal neuronal culture model, providing a possible explanation for the observed seizure discharge and enhanced excitability in epilepsy., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Impaired GABAergic inhibitory synaptic transmission plays an essential role in the pathogenesis of selective neuronal cell death following transient global ischemia. GABA(A) receptor (GABA(A)R), K⁺-Cl⁻ co-transporter 2 (KCC2), Na⁺-K⁺-Cl⁻ co-transporter 1 (NKCC1) and astrocytes are of particular importance to GABAergic transmission. The present study was designed to explore whether the neuroprotective effect of topiramate (TPM) was linked with the alterations of GABAergic signaling and astrocytes. The bilateral carotid arteries were occluded, and TPM (80 mg/kg/day (divided twice daily), i.p.) was injected into gerbils. At day 1, 3 and 7 post-ischemia, neurological deficit was scored and changes in hippocampal neuronal cell death were evaluated by Nissl staining. The apoptosis-related regulatory proteins (procaspase-3, caspase-3, Bax and Bcl-2) and GABAergic signal molecules (GABA(A)R α1, GABA(A)R γ2, KCC2 and NKCC1) were also detected using western blot assay. In addition, the fluorescent intensity and protein level of glial fibrillary acidic protein (GFAP), a major component of astrocyte, were examined by confocal and immunoblot analysis. Our results showed that TPM treatment significantly decreased neurological deficit scores, attenuated the ischemia-induced neuronal loss and remarkably decreased the expression levels of procaspase-3, caspase-3 as well as the ratio of Bax/Bcl-2. Besides, treatment with TPM also resulted in the increased protein expressions of GABA(A)R α1, GABA(A)R γ2 and KCC2 together with the decreased protein level of NKCC1 in gerbils hippocampus. Furthermore, fluorescent intensity and protein level of GFAP were evidently reduced in TPM-treated gerbils. These findings suggest that the therapeutic effect of TPM on global ischemia/reperfusion injury appears to be associated with the enhancement of GABAergic signaling and the inhibition of astrogliosis in gerbils., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

From defensive skin secretions acquired from two species of African hyperoliid frogs, Kassina maculata and Kassina senegalensis, we have isolated two structurally related, C-terminally amidated tridecapeptides of novel primary structure that exhibit a broad spectrum of biological activity. In reflection of their structural novelty and species of origin, we named the peptides kassorin M (FLEGLLNTVTGLLamide; 1387.8 Da) and kassorin S (FLGGILNTITGLLamide; 1329.8 Da), respectively. The primary structure and organisation of the biosynthetic precursors of kassorins M and S were deduced from cloned skin secretion-derived cDNA. Both open-reading frames encoded a single copy of kassorin M and S, respectively, located at the C-terminus. Kassorins display limited structural similarities to vespid chemotactic peptides (7/13 residues), temporin A (5/13 residues), the N-terminus of Lv-ranaspumin, a foam nest surfactant protein of the frog, Leptodactylus vastus, and an N-terminal domain of the equine sweat surfactant protein, latherin. Both peptides elicit histamine release from rat peritoneal mast cells. However, while kassorin S was found to possess antibacterial activity against Staphylococcus aureus, kassorin M was devoid of such activity. In contrast, kassorin M was found to contract the smooth muscle of guinea pig urinary bladder (EC(50) = 4.66 nM) and kassorin S was devoid of this activity. Kassorins thus represent the prototypes of a novel family of peptides from the amphibian innate immune system as occurring in defensive skin secretions., (Copyright © 2010 Elsevier Ltd. All rights reserved.)