Investigation of action of enkephalin on the spontaneous and evoked release of acetylcholine from rat cortical and striatal slices.

1 The effects of two synthetic enkephalins, D-Ala2-Met5-enkephalinamide (DALA) and D-Ala2-MePhe4-Met5-(0)-ol-enkephalin (33,824) were tested on the spontaneous and stimulated release of acetylcholine (ACh) from rat cortical and striatal slices. 2 DALA, but not 33,824, caused a modest increase in spontaneous cortical ACh release. Neither enkephalin affected the release of cortical ACh induced by high potassium (25 mM) or veratridine (20 microM). 3 DALA had no effect on the release of ACh from striatal slices occurring spontaneously or in the presence of potassium (25 mM), veratridine (5 microM) or ouabain (10 microM). The enkephalin 33,824 also had no significant action on the striatal ACh release except that it caused a slight enhancement of veratridine-evoked release. 4 It is suggested that enkephalins have no significant action on release of ACh from the cortex or striatum in vitro. Their action on ACh release from the cortex in vivo, seen in previous studies, may be exerted at a subcortical level.