Preferential action of beta-bungarotoxin at nerve terminal regions in the hippocampus

The action of beta-bungarotoxin on the transverse slice of rat hippocampus has been studied in vitro. The toxin (230 nM) initially impaired neurotransmission in the major subdivisions of the slice with a half time for blockade of about 10 min. Intracellular recordings revealed no reduction in pyramidal cell sensitivity to putative neurotransmitters, suggesting a primary action of the toxin upon transmitter release. More protracted effects of beta-bungarotoxin included a reduction of neuronal excitability, particularly in the terminal regions of hippocampal fibre pathways, but these proceeded at a much slower rate than the action on synaptic transmission. It is concluded that the toxin binds to some component present at terminal regions to mediate its preferential effect in the hippocampus.