Does dopamine suppress stress-induced intestinal and renal vasoconstriction?

Dopamine interference with intestinal and renal sympathetic reflex vasoconstrictor responses was studied in cats anaesthetized with diazepam, fentanyl and nitrous oxide. Vasoconstriction was induced by electric stimulation of the hypothalamic defence-alarm area and by stimulation of somatic and visceral afferents. In addition, intestinal vasoconstriction was elicited by direct stimulation of postganglionic sympathetic efferent nerves. In the intestine, dopamine administration (7.5 microgram X kg-1 X min-1) was not associated with an attenuation of the investigated sympathetic vasoconstrictor responses, although dopamine per se decreased intestinal vascular resistance by 36 +/- 4%. Due to this dopamine-induced background vasodilation, the intestinal blood flow level during stimulation procedures and concomitant dopamine infusion was higher than during similar stimulations prior to dopamine (for defence-alarm area stimulation 45 +/- 16%, for afferent nerve stimulation 79 +/- 22% and for efferent postganglionic nerve stimulation 66 +/- 16%). In the kidney, dopamine per se had only minor effects on vascular resistance and on changes in vascular tone elicited by the stimulation procedures. The renal blood flow level in response to the stimulation procedures was not significantly affected by dopamine. In conclusion, dopamine may contribute to a sustained intestinal blood flow level when administered during supervening stress-related sympathetic activation.