CHOLINERGIC ACTION IN THE NUCLEUS ACCUMBENS: MODULATION OF DOPAMINE AND ACETYLCHOLINE RELEASE

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Abstract
1 The action of oxotremorine and acetylcholine on the release of dopamine and acetylcholine from tissue slices of the rat nucleus accumbens was studied. 2 Oxotremorine significantly enhanced the release of [14C]-dopamine evoked by 34 mmK+ and the EC50 for this action was 1.5 × 10−7 m. A maximal enhancement (30%) for this effect was reached at 2 × 10−7 m oxotremorine. A further enhancement of dopamine release occurred at concentrations of oxotremorine greater than 10−4 m. 3 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). 4 Oxotremorine affected [3H]-acetylcholine release differentially, inhibiting the K+-evoked release of [3H]-acetylcholine at concentrations greater than 10−5m. The IC50 for this process was 4.3×10−5m. 5 Acetylcholine (8 × 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%). 6 The mechanism of action of oxotremorine on dopamine release is discussed in terms of a presynaptic receptor-mediated process.