Ghrelin is a pleiotropic neuropeptide that has been recently implicated in epilepsy. Animal studies performed to date indicate that ghrelin has anticonvulsant properties; however, its mechanism of anticonvulsant action is unknown. Here we show that the anticonvulsant effects of ghrelin are mediated via the growth hormone secretagogue receptor (GHSR). To our surprise, however, we found that the GHSR knockout mice had a higher seizure threshold than their wild-type littermates when treated with pilocarpine. Using both in vivo and in vitro models, we further discovered that inverse agonism and desensitization/internalization of the GHSR attenuate limbic seizures in rats and epileptiform activity in hippocampal slices. This constitutes a novel mechanism of anticonvulsant action, whereby an endogenous agonist reduces the activity of a constitutively active receptor.

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SUMMARYNeuropeptides appear to be of importance when the central nervous system (CNS) is challenged, such as during high-frequency firing and pathologic conditions. Potential advantages of treatments that target neuropeptide systems in comparison to classical neurotransmitter systems and ion channels revolve around the subject of efficacy as well as the reduced likelihood of side effects, thus making them attractive candidates for the development of new clinical applications for various disorders. The number of neuropeptides linked to epilepsy is on the rise, reflecting the increased interest of researchers in this domain. Ghrelin has only very recently been introduced into the field of epilepsy, and has already led to contradictory clinical publications. There is a great paucity with regard to what mechanism of action is utilized by ghrelin to inhibit seizures. In this review we disclose how we can better understand the mechanism ghrelin uses to prevent seizures, which indirectly could give an insight to researchers who are studying ghrelin in other fields of research.

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