Influence of naloxone on the captopril-induced decrease in vagal pressor reflexes.

The effects of intracisternal injection of captopril (0.3 mg/kg) on the pressor responses elicited by afferent stimulation of the vagus were investigated in the anaesthetized dog. The captopril-induced decrease in the systolo-diastolic pressor response to vagal stimulation was reversed by subsequent injection of naloxone (0.1 mg/kg, i.v.). These results suggest the involvement of central opioid mechanisms in the hypotensive properties of captopril.