Cerebral vascular responsiveness in deoxycorticosterone acetate-salt hypertensive rats

Alterations in cerebral vascular responsiveness were investigated in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Initial studies on the passive-force response characteristics of strips of basilar artery revealed no difference between control and DOCA-salt rats. No difference in acetylcholine-induced relaxation was seen between the two groups. The contractile response to KCl was similar in control and DOCA-salt rats. An increase in both threshold and midrange sensitivities to serotonin (5-HT) was seen in basilar artery from DOCA-salt rats. However, extracellular Ca sensitivity in the presence of 10(-6) M 5-HT was not altered. Intracellular Ca release (phasic contraction in response to 10(-6) M 5-HT) was similar in control and DOCA-salt rats. Relaxation in response to Ca (membrane stabilization) was also not different. Whereas sodium nitroprusside (SNP)-induced relaxation was not altered in basilar artery from DOCA-salt rats, a significant decrease in isoproterenol (ISO)-induced relaxation was observed. Relaxation following washout of maximal contractions to KCl and 5-HT was similar in the two groups. These results demonstrate specific alterations in cerebral vascular responsiveness of DOCA-salt rats. Whereas KCl contractile and SNP relaxation responses were not affected, responses to 5-HT and ISO were significantly altered. These changes do not appear to be related to alterations in the endothelium or in the Ca responsiveness of the vascular smooth muscle.