THE HYPOTENSIVE EFFECTS OF INTRACEREBROVENTRICULARLY ADMINISTERED DOPAMINE-3-O-SULFATE IN ANESTHETIZED RATS

We previously reported that dopamine (DA)-4-O-sulfate increased contra ctile force in a dose dependent manner but that synthesized DA-3-O-sul fate had no any significant effects on rabbit papillary muscle. In thi s study, we have looked into the vascular effect of the DA-sulfates. D A-4-O-sulfate produced a dose-dependent vasoconstriction on isolated r at aorta and this vasoconstriction was significantly inhibited by praz osin, domperidone and verapamil. The intravenous administration of DA- 4-O-sulfate increased rat blood pressure in a dose-dependent manner. T his presser effect was also significantly inhibited by bunazosin, yohi mbine and verapamil. Intracerebraoventricular (i.c.v.) injection of DA -4-O-sulfate caused an increase in blood pressure, which was followed by a decrease. DA-3-O-sulfate (i.c.v) produced a significant decrease in the blood pressure of rats. The responses to DA-CO-sulfate and DA-3 -O-sulfate were significantly inhibited by clonidine. This is the firs t report that DA-3-O-sulfate has a centrally active depressor effect. These results suggest that central DA-sulfates regulate blood pressure in addition to the intermediating in the catecholamine metabolism.