Hypotensive effects of captopril administered centrally in intace conscious spontanously hypertensive rats and peripherally in anephric anaesthetized spontaneously hypertensive rats.

1. The hypotensive response to captopril in anaesthetized spontanously hypertensive rats (SHR) is not modified by bilateral nephrectomy performed 1 or 24 h previously. 2. Intracerebroventricular injection (i.c.v.) of captopril (2 mg kg-1) significantly lowered blood pressure of conscious SHR over a 7-h period of observation but there was no significant blood pressure response to i.c.v. vehicle, or to intravenous captopril (2 mg kg-1) in SHR. 3. There was no significant blood pressure response to captopril (2 mg kg-1) i.c.v. in the normotensive Wistar Kyoto controls (NT-WK). 4. These results indicate that captopril can lower the blood pressure of SHR by mechanisms independent of the kidneys or the circulating renin-angiotensin system. 5. The hypotensive effect of central captopril in SHR but not in the NT-WK suggests biochemical differences between the brains of the two rat strains.