Inhibition of central angiotensin I conversion by oral captopril.

1. The central action of captopril (D-3-mercapto-methylpropanoyl-L-proline, SQ 14225) in the rat was evaluated by measuring the effect of the orally administered drug on responses to angiotensin I given intracerebroventricularly. 2. The pressor and dipsogenic effects of angiotensin I (20 ng) injected into the third ventricle were reduced by about 50% for 4 h following the oral administration of captopril, 20mg/kg. Both responses returned to pretreatment control values 8 h after captopril administration. 3. Orally administered captopril affects the action of angiotensin I on the central nervous system thus providing an alternative explanation for the hypotensive effect of captopril. This effect if probably due to the direct passage of captopril through the blood brain barrier.