Effects of iontophoretic application of convulsants on the sensory responses of neurons in the brain-stem reticular formation.

Iontophoretic or pneumatic application of convulsants produced enhancement of the sensory responses of brain-stem reticular formation (RF) neurons in cat and rat. Enhanced sensory responsiveness is observed with visual, auditory, somatosensory and vibrissa manipulation following application of strychnine, bicuculline or pentylenetetrazol. The effect was not transmitter-specific, since it could be produced by sequential application of bicuculline and strychnine which are thought to affect different neurotransmitters. Intravenous administration of convulsant also enhanced the responsiveness of RF neurons which had previously been affected by application of a different convulsant. Both systemic and iontophoretic effects could be antagonized by application of GABA and glycine. These data, coupled with previous findings in primary sensory pathways, indicate that sensory response enhancement in the RF induced by intravenous administration of these convulsants is in large part due to actions on synaptic elements of reticular formation neurons.