Cholinergic action in the nucleus accumbens: modulation of dopamine and acetylcholine release.

The action of oxotremorine and acetylcholine on the release of dopamine and acetylcholine from tissue slices of the rat nucleus accumbens was studied. Oxotremorine significantly enhanced the release of [14C]-dopamine evoked by 34 mMK+ and the EC50 for this action was 1.5 X 10(-7)M. A maximal enhancement (30%) for this effect was reached at 2 X 10(-7)M oxotremorine. A further enhancement of dopamine release occurred at concentrations of oxotremorine greater than 10(-4)M. The action of oxotremorine on [14C]-dopamine release was calcium-dependent and blocked by atropine (10(-4) M) but not mecamylamine (up to 10(-4) M). Oxotremorine affected [3H]-acetylcholine release differentially, inhibiting the K+-evoked release of [3H]-acetylcholine at concentrations greater than 10(-5) M. The IC50 for this process was 4.3 X 10(-5) M. Acetylcholine (8 X 10(-4) M) showed a similar pattern of action to oxotremorine: it enhanced the K+-evoked release of [14C]-dopamine (50%) and inhibited the K+-evoked release of [3H]-acetylcholine (30%). The mechanism of action of oxotremorine on dopamine release is discussed in terms of a presynaptic receptor-mediated process.