The effects of the acute and chronic administration of chlordiazepoxide on spontaneous motility and on the reactivity of the generator of embryonic motility were studied in chick embryos from the 4th to the 19th day of incubation. 1. The acute administration of chlordiazepoxide (5 mg/kg e.w.) significantly depressed spontaneous motility from the 13th day of incubation. 2. The chronic administration of chlordiazepoxide (12.2 mg/kg e.w./24 h) from the 4th to the 8th, 12th and 16th day of incubation enhanced the reduction of the spontaneous motility of 17-day-old embryos. 3. The chronic administration of chlordiazepoxide significantly modified the activity of both activators (strychnine, metrazol, bicuculline, picrotoxin) and inhibitors (GABA, chlordiazepoxide) of the spontaneous motility of chick embryos.

Research Laboratory of Psychiatry Faculty of Medicine Charles University Prague