The interaction between metoclopramide and dopaminergic agonists at the level of sympathetic ganglion.

The interaction of metoclopramide and two dopaminergic agonists, dopamine and apomorphine, was investigated on ganglionic transmission at the superior cervical ganglion of the anaesthetized cat. Dopamine (100 micrograms, i.a.) and apomorphine (100 micrograms, i.a.) decreased the height of action potential induced by supramaximal preganglionic stimulation. Metoclopramide (3 mg/kg, i.v.) antagonized the inhibition caused by dopamine and apomorphine. But it did not alter the transmission block caused by hexamethonium (100 micrograms, i.a.) or noradrenaline (100 micrograms, i.a.). The results suggest that dopamine-induced inhibition of the ganglionic transmission is related to the activation of dopaminergic receptors of the ganglion cells.