δ 1‐OPIOID receptor‐mediated controlofacetylcholine (ACh) release in human neocortex slices

In slices of human neocortex, prelabelled with [3H]-choline, the release of [3H]-acetylcholine reflects the evoked release of endogenous acetylcholine which was elicited by the same electrical stimulation paradigm. [3H]-Acetylcholine release was depressed by the delta-opioid receptor agonist D-Pen2-D-Pen5-enkephalin. When the nerve endings were depolarized by elevating extracellular potassium the evoked [3H]-acetylcholine release was similarly depressed by D-Pen2-D-Pen5-enkephalin in the absence, but not in the presence, of tetrodotoxin which blocks action potential propagation. Therefore, the delta-opioid receptor inhibiting [3H]-acetylcholine release should not be located to cholinergic n…