[Plasma renin activity and prostaglandin E2 in hypotension induced by nicergoline]

The hypotensive actions of nicergoline, a new alpha 1-adrenoreceptor blocking agent, were studied in six dogs during stable anaesthesia under mechanical ventilation. Systemic haemodynamic parameters were measured before the infusion of nicergoline (500 micrograms X kg-1 in 5 min), and regularly after it during 2 h. Plasma renin activity (PRA), right atrial (V PGE2) and arterial (A PGE2) prostaglandin E2 concentrations measured by radio-immunoassay were collected before, and 10 and 20 min after nicergoline infusion. The mean aortic pressure fell to its lowest figure (-30%) at the 5th min, this being maintained for 45 min. Heart rate and cardiac output remained unchanged. Pulmonary wedge pressure (p less than 0.01) and central venous pressure (p less than 0.05) decreased. All parameters reached their control values in 120 min. PRA was unchanged. V PGE2 (p less than 0.01) and pulmonary extraction in PGE2 (V PGE2 - A PGE2/V PGE2) (p less than 0,05) increased whilst A PGE2 was unmodified. The fall in mean aortic pressure was linked (p less than 0.001) to the increase in V PGE2. Nicergoline infusion induced hypotension by reducing vascular tone of resistance and capacitance beds. Hypotension was related to the vasoplegia and to an inhibition of the rapid pressor control mechanisms. The reasons for the lack of renin release were unknown. V PGE2 release was stimulated by the hypotension. The increase in pulmonary extraction in PGE2 was involved in the maintenance of A PGE2 concentration. Nicergoline gave mild hypotension without reflex sympathetic activation. Its alpha-adrenoreceptor blocking properties were similar to those of prazosin.(ABSTRACT TRUNCATED AT 250 WORDS)