Long-term changes in sensitivity to GABA in dorsal raphe neurons following amygdala kindling

The present experiments were undertaken to evaluate GABA sensitivity in dorsal raphe neurons following amygdala-kindled seizures. Dorsal raphe neurons of amygdala-kindled rats exhibited significant subsensitivity to GABA as measured electrophysiologically 3 or 4 weeks after the last stage 5 seizure. Amygdala stimulation with currents which did not produce kindled seizures did not produce subsensitivity to GABA. The subsensitivity observed after kindling was equivalent in magnitude to that observed following chronic diazepam treatment. However, exposure of fully kindled rats to chronic diazepam did not further decrease the sensitivity of dorsal raphe neurons to GABA. Additionally, while subsensitivity to GABA was reversed by bath application of the benzodiazepine antagonist, Ro 15-1788, in chronic diazepam-treated rats, it had no effect on GABA subsensitivity in fully kindled rats. These findings suggest a decrease in GABA sensitivity within the dorsal raphe might reflect long-term neuronal changes associated with kindled seizures. These data also suggest that the decrease in GABA sensitivity of dorsal raphe neurons following chronic diazepam may involve different mechanisms from those observed after amygdala kindling.