Dopamine decreases quantal output in mouse muscles

Dopamine was found to reduce the quantal content of end-plate potentials in cut-fiber preparations of mouse diaphragm but not in Mg2+-blocked preparations. Possible mechanisms for this effect include reduction of the presynaptic store of acetylcholine available for release, or blockade by dopamine of a positive feedback on acetylcholine release, possibly mediated by muscarinic receptors on nerve terminals.