In vivo and in vitro dopaminergic effects of three ergoline fragments.

The pharmacological effects of three ergoline fragments (BD-179, BD-271 and BD-214) were studied in vivo using the cat cardioaccelerator nerve preparation and in vitro using field stimulated isolated cat right atria. BD-179 and BD-271 produced dose dependent inhibition of tachycardia due to electrical stimulation of the right postganglionic cardioaccelerator nerve in anesthetized cats, BD-214 was inactive. BD-179 produced primarily hypotension, BD-271 produced a transient pressor response followed by hypotension and BD-214 produced only pressor effects. The tachycardia inhibitory effects and hypotension produced by BD-179 and BD-271 were antagonized by the dopamine receptor antagonist sulpiride. BD-179, BD-271 and BD-214 antagonized the presynaptic inhibitory effects of the dopamine receptor agonist apomorphine in vitro on field stimulated isolated cat right atria. All three ergoline fragments facilitated stimulation-induced increases in systolic tension development and BD-214 facilitated stimulation-induced tachycardia in isolated cat right atria.