Voltage-gated, margatoxin-sensitive potassium channels, but not calcium-gated, iberiotoxin-sensitive potassium channels modulate acetylcholine release in rat striatal slices

We evaluated the effects of iberiotoxin, an inhibitor of Slo-type Ca2+-activated potassium channels and two inhibitors of Shaker-type voltage-gated potassium channels margatoxin and dendrotoxin on acetylcholine outflow in rat striatal slices. An in vitro perfusion with 100 nM margatoxin or dendrotoxin induced a concentration-dependent and tetrodotoxin-sensitive enhancement in spontaneous acetylcholine release. in contrast, a perfusion with iberiotoxin did neither modulate basal, nor electrically- or N-methyl-d-aspartate-induced transmitter release. Therefore, Slo-type Ca2+-activated Kt-channels do not seem to contribute significantly to cholinergic neurotransmission within rat striatal slices. As the Kv1.2 subtype represents the only common high affinity binding site of margatoxin and dendrotoxin and the effects of these toxins are not additive, this subtype is suggested to be the channel utilized by margatoxin and dendrotoxin to release acetylcholine in this model. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.