Endogenous anticonvulsant substance in rat cerebrospinal fluid after a generalized seizure.

Cerebrospinal fluid taken from rats subjected to electroshock-induced seizures and injected into the cerebral ventricles of rats that had not been shocked increased the seizure threshold of the recipients. The anticonvulsant activity of the donor cerebrospinal fluid was antagonized by opioid antagonists and enhanced by peptidase inhibitors. These results suggest the existence of an endogenous anticonvulsant substance in rat cerebrospinal fluid, possibly opioid in nature, which is activated as a consequence of a seizure and which may play a critical role in postseizure inhibition.