Generation of the Seizure Discharge in Thin Sections From the Guinea Pig Brain in Chloride-Free Medium in Vitro

1.Electrical activities of the thin sections prepared from the guinea pig hippocampus were studied in vitro in artificial media of modified composition.2.When Cl ion in the medium was substituted with large anions (such as propionate ion), a train of afterdischarge consisting of large spike potentials and superposed on a slow wave was elicited by a single shock applied to the section.The spontaneous discharges were observed as well.3.The discharge propagated through the slice at a speed of 1 to 3cm/sec.4.A complete silence of electrical activities (post-afterdischarge extinction) followed the afterdischarge in some stage of the experiments.5.The discharge was augmented by phenobarbital sodium in low concentrations but suppressed in high concentrations of the anesthetic.6.The discharge was found to originate in the dentate gyrus.7.It was concluded that the discharge was akin to the seizure discharge. Its generation in the present experimental condition was considered due to suppression of inhibitory mechanisms.