Interaction of topiramate with glycine receptor channels

Inhibition of miR-203 Reduces Spontaneous Recurrent Seizures in Mice

Inhibitory synaptic receptors are dysfunctional in epileptic brains, and agents that selectively target these receptors may be effective for the treatment of epilepsy. MicroRNAs interfere with the translation of target genes, including various synaptic proteins. Here, we show that miR-203 regulates glycine receptor-β (Glrb) in epilepsy models. miR-203 is upregulated in the hippocampus of epileptic mice and human epileptic brains and is predicted to target inhibitory synaptic receptors, including Glrb. In vitro transfection, target gene luciferase assays, and analysis of human samples confirmed the direct inhibition of GLRB by miR-203, and AM203, an antagomir targeting miR-203, reversed the effect of miR-203. When intranasal AM203 was administered, AM203 reached the brain and restored hippocampal GLRB levels in epileptic mice. Finally, intranasal AM203 reduced the epileptic seizure frequency of mice. Overall, this study suggests that GLRB expression in the epileptic brain is controlled by miR-203, and intranasal delivery of AM203 showed therapeutic effects in chronic epilepsy mice.

Molecular and genetic determinants of alcohol dependence

Alcohol dependence is a complex disorder affecting all social and ethnic groups. Although the scientific understanding of the mechanism governing this multifactorial disease is still in its infancy, understanding its biological bases, including the potential contribution of genetic factors, is key to characterizing individual's risk and developing efficacious therapeutic target to combat the disease. This review provides an overview of different approaches that are being increasingly integrated to extend our knowledge of the genetic underpinnings of alcohol dependence.

Substantia Nigra Is an Anticonvulsant Site of Action of Topiramate in the Focal Pilocarpine Model of Limbic Seizures

PURPOSE

The substantia nigra pars reticulata (SNR) is known to play a role in gating and control of seizures. Prompted by the observation that intrahippocampal topiramate (TPM) administration does not suppress limbic seizures in the focal pilocarpine model, we investigated the role of the SNR in the anticonvulsant mechanism of action of TPM.

METHODS

Limbic seizures were evoked in freely moving rats by intrahippocampal administration of pilocarpine via a microdialysis probe. Changes in hippocampal extracellular (EC) glutamate and GABA concentrations were monitored. Effects of intraperitoneal (10-200 mg/kg), intrahippocampal (1-5 mM), and bilateral intranigral (100-300 nmol) TPM administration on pilocarpine-induced seizures and neurochemical changes were evaluated. Effects of TPM administration alone on hippocampal and nigral EC amino acid concentrations were also studied.

RESULTS

Systemic and intranigral, but not intrahippocampal TPM administration suppressed pilocarpine-induced seizures and neurochemical changes. Nigral GABA(A) receptor blockade by picrotoxin abolished the anticonvulsant effect of TPM in SNR. Systemic TPM administration increased hippocampal glutamate and decreased GABA. Intranigral TPM administration increased hippocampal glutamate, but not GABA. Intrahippocampal TPM increased hippocampal glutamate and GABA, but only at high concentrations.

CONCLUSIONS

In the focal pilocarpine model, TPM does not exert its anticonvulsant effect at the site of seizure initiation. We identified the SNR as a site of action of TPM, and showed that the nigral GABA-ergic system is central to TPM's anticonvulsant effect in SNR. Anticonvulsant effects and neurochemical changes in hippocampus following intranigral TPM administration suggest the existence of a nigro-hippocampal circuit, which may be involved in the control of limbic seizures.