Bicuculline-induced enhancement of sensory responses and cross-correlations between reticular formation and cortical neurons.

The visual, auditory and somatosensory responses of neurons in the brain stem reticular formation (RF) and pericruciate cortex of the cat are enhanced by intravenous administration of subconvulsant doses of bicuculline. The degree of enhancement in RF neurons is somewhat greater in magnitude and occurs in a greater percentage of RF neurons. The latency of response is shorter in the RF than in the cortex in 70% of cases. A large percentage of simultaneously recorded RF and cortical neurons which became responsive to the same stimulus exhibited consistent convulsant-induced cross-correlations of firing which were not present before drug treatment. The latency and correlation data are consistent with the possibility that the RF may subserve the cortical enhancement. Auditory response thresholds in RF neurons are reduced by bicuculline administration. Enhancement of RF neuronal responsiveness has previously been observed with several other convulsant drugs which are thought to act on different neurotransmitters suggesting that it may reflect a general action of these agents beyond the effects on specific neurotransmitters. The bicuculline-induced correlation of firing of RF and pericruciate neurons may be involved in the mechanism of initiation of convulsant-mediated seizure generalization induced by sensory stimuli.