Abstract
Abstract
The effect of cerebral intraventricular administration of 6-hydroxydopamine (6-OHDA) on blood pressure and vascular smooth muscle responsiveness in deoxycorticosterone acetate (DOCA)-treated rats was assessed. Rats treated with 6-OHDA and DOCA had significantly lower systolic blood pressures (142 ± 8 mm Hg) than rats treated with DOCA alone (185 ± 5 mm Hg). After 5 weeks of DOCA treatment, femoral arteries and aortae were excised from these rats, cut helically into strips, and placed in a muscle bath to record isometric force. Dose-response curves to serotonin were shifted to the left in femoral arteries from DOCA-treated rats compared to both control and 6-OHDA-DOCA-treated rats (ED50: DOCA = 6.8 × 10−8 M, control = 27.9 × 10−8 M, 6-OHDA-DOCA = 13.4 × 10−8 M). Arachidonic acid, the prostaglandin precursor, produced greater maximal contractions in femoral artery strips of DOCA-treated rats (358 ± 56 mg) than in those from controls (115 ± 31 mg). The maximal response to arachidonic acid in arteries from 6-OHDA-DOCA rats (203 ± 78 mg) was not different from control values. Ouabain produced a greater maximal response in aortic strips from DOCA rats (658 ± 165 mg) compared to those from control (196 ± 72 mg) or 6-OHDA-DOCA (309 ± 87 mg) rats. We conclude that increased vascular responsiveness to serotonin, arachidonic acid, and ouabain in DOCA hypertensive rats is secondary to a central action of the mineralocorticoid.
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