PURINERGIC MODULATION OF HIPPOCAMPAL ACETYLCHOLINE-RELEASE INVOLVES ALPHA-DENDROTOXIN-SENSITIVE POTASSIUM CHANNELS

Abstract: Modulation of acetylcholine (ACh) release from superfused hippocampal slices was examined when the release of ACh was stimulated by exposure of slices to elevated K+ concentration. Evoked release was not sensitive to inhibition by 0.1 μM tetrodotoxin, but it could be inhibited in a dose‐dependent manner by a muscarinic agonist (10–100 nM oxotremorine) and a purinergic agonist (10–100 nM 2‐chloroadenosine). The α‐dendrotoxin (100 nM), which selectively blocks voltage‐gated inactivating K+ channels in nerve endings, did not affect the release of ACh under resting or depolarized conditions. However, α‐dendrotoxin reduced the 2‐chloroadenosine‐induced inhibition of release, but did not alter the oxotremorine‐induced inhibition. These results suggest that an α‐dendrotoxin‐sensitive K+ channel may be activated as an obligatory step in the modulation of ACh release by presynaptic purinergic receptor activation, but not in the modulation by presynaptic muscarinic receptors. Copyright © 1990, Wiley Blackwell. All rights reserved