Behavioral effects of bicuculline microinjection in the dorsal versus ventral hippocampal formation of rats, and control of seizures by nigral muscimol.

This work aims to describe behavioral/electroencephalographic (EEG) seizures induced by bicuculline microinjection intracerebroventricularly (ICV) and in the dorsal hippocampal formation (DHF) or ventral hippocampal formation/amygdala area (VHF-AMY). We also test if GABAergic manipulation in the substantia nigra pars reticulata (SNPR) is capable of controlling those seizures. ICV injection of bicuculline induced a progressive sequence of convulsive responses, jumps and escapes from the open-field. This effect was partially reached by bicuculline injection in the DHF or VHF-AMY injection. Also: muscimol injection, but not GABA uptake blockers (nipecotic acid or a spider venom neurotoxin FrPbA2), into the SNPR abolished seizures induced by bicuculline injection in the DHF. It was concluded that different neuronal circuitry in the hippocampal formation are modulated, at least partially by nigral GABAergic mechanisms.