Cardiovascular actions of the dopamine receptor agonist Z1046 in swine.

Dopamine receptor agonists can be useful in the treatment of hypertension or heart failure. Consequently, the present study investigated the hemodynamic profile of the novel dopamine D1/D2 receptor agonist Z1046 in open-chest, pentobarbital-anesthetized swine. Z1046 was administered in a dose of 10 micrograms/kg (n = 9) or 100 micrograms/kg (n = 8), which was injected over 1 minute; hemodynamic responses were studied for 90 minutes after administration. Both doses of Z1046 produced sustained decreases in mean aortic blood pressure (15-20%). The hypotension produced by the lower dose was principally due to a decrease in cardiac output, as the trend toward a lower systemic vascular resistance failed to reach levels of statistical significance. Conversely, the decrease in mean arterial blood pressure produced by the higher dose of Z1046 was mainly due to a decrease in systemic vascular resistance (up to 17%), as the trend toward a decrease in cardiac output at 60 and 90 minutes after administration was not different from the changes in the saline-treated group. Heart rate decreased slightly with both doses of Z1046. Z1046 decreased left ventricular myocardial blood flow (up to 28 +/- 9%, p < 0.05) in parallel with the decrease in myocardial oxygen consumption (up to 24 +/- 7%, p < 0.05), with no change in the transmural distribution of myocardial blood. Z1046 in a dose of 10 micrograms/kg did not produce significant vasodilation of regional vascular beds, but in a dose of 100 micrograms/kg produced vasodilator responses in the small intestine (34 +/- 2% decrease in vascular resistance), spleen (43 +/- 7%), and kidneys (22 +/- 3% all p < 0.05 vs. baseline). In conclusion, Z1046 produced systemic hypotension with negligible reflex activation of sympathetic tone.