Chronotropic effect of tyramine on rat heart cells cultured with sympathetic neurons

Dissociated newborn rat superior cervical ganglion neurons in culture without exogenous nerve growth factor survive and extend processes on a monolayer of rat heart ventricular cells. An increase in the contraction rate of the heart cells was observed in 83% of the co-cultures treated with 5 X 10(-6) M tyramine. No increase was seen in heart cell cultures without neurons. These results are consistent with the assumed mode of action of tyramine--the release of catecholamines from nerve terminals--and suggest that functional interaction can occur in culture between sympathetic neurons and heart ventricular cells.