Dopaminergic activity of a nonhydroxylated aminotetralin derivative (TL-68) on cat hearts

An aminotetralin derivative, N,N-dipropyl-2-amino-1,2,3,4 tetrahydronaphtelene (TL-68) produced dose- and concentration-dependent inhibition of heart rate increases induced by stimulation of the cardioaccelerator nerves of anesthetized cats and by transmural stimulation of isolated cat right atria. These inhibitions were reversed by the dopaminergic antagonist haloperidol and not by the alpha2 adrenergic antagonist yohimbine. Results suggest that TL-68-induced inhibition of heart rate responses to stimulation of postganglionic sympathetic nerve endings is by stimulation of presynaptic inhibitory dopaminergic receptors in cat hearts. Since the compound is active in both in vivo and in vitro experiments, TL-68 apparently does not require metabolic activation before interaction with dopaminergic receptors.