| Abstract: | 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. |
