Increased susceptibility of detelencephalated rats to audiogenic seizures induced by microinjection of bicuculline into the inferior colliculus

ABSTRACT

The participation of telencephalic forebrain structures in the induction of audiogenic seizure (AGS) susceptibility and in the behavioral expression of AGS was investigated in rats. Rats that were initially susceptible (N = 12) or non-susceptible (N = 28) to audiogenic seizure were surgically detelencephalated. A unilateral microinjection of a low dose (30 pmol) of the GABA antagonist bicuculline methiodide (BM) was applied to the inferior colliculus (IC) before the animals were exposed to a 120-dB acoustic stimulus. All susceptible rats still exhibited all components of audiogenic seizure after removal of the telencephalon. After BM microinjection, a higher incidence (66% vs 41%) and shorter latencies (6-20 s vs 9-55) s) of occurrence of tonic seizures were observed in the detelencephalated non-susceptible rats when compared to non-operated non-susceptible rats(N = 12). These results suggest that the induction of the behavioral expression of audiogenic seizures issubserved by brain stem neuronal networks but does not require the telencephalon and that telencephalic structures may exert control over audiogenic seizures by inhibiting IC cells through GABAergic neurons