Hemodynamic effects of two ergot derivatives in the conscious spontaneously hypertensive rat

The effect of acute and chronic administration of two ergot derivatives, dihydroergosine (DHESN) and ergosinine (ESNN), on blood pressure, heart rate, cardiac output and total peripheral resistance was studied in conscious spontaneously hypertensive rats. Acute administration of either DHESN or ESNN (50-100 micrograms/kg) resulted in prompt and significant (p less than 0.01) decrease of both blood pressure and heart rate, which lasted for more than 12 h. The decrease in blood pressure was due to reduction in total peripheral resistance, as cardiac output remained unchanged. Prolonged treatment (50 micrograms/kg, i.p., every second day for 12 days) with either DHESN or ESNN significantly (p less than 0.01) decreased blood pressure. In chronically treated rats, total peripheral resistance was found to be decreased while no changes in cardiac output and heart rate were observed. The results indicate that both DHESN and ESNN are potent antihypertensive agents, due to their vasodilator effects. The hypotensive effect of DHESN could be partially blocked by haloperidol, but not by yohimbine. Both, DHESN and ESNN antagonized the effect of phenylephrine on blood pressure.