Pressor and depressor responses to intracerebroventricularly administered prostaglandins and arachidonic acid in anaesthetized rabbits

Abstract

The effects of intracerebroventricularly (i.c.v.) administered prostaglandin (PG) E₂, F_2α, I₂ and their precursor, arachidonic acid (AA), on systemic blood pressure were investigated in anaesthetized rabbits. 1) PGE₂ (0.03-1 μg/ 0.1 ml/rabbit) elevated blood pressure in a dose-related manner. 2) PGF_2α exerted no significant changes on blood pressure. 3) PGI₂ (0.3-10 μg/0.1 ml/rabbit) lowered blood pressure in a dose-related manner. 4) AA (0.1-10 μg/0.1 ml/rabbit) dose-independently elevated blood pressure. 5) I.c.v. pretreatment with indomethacin, an inhibitor of cyclooxygenase, abolished the hypertensive effect of AA, but did not influence the hypertensive and hypotensive effect caused by PGE₂ and PGI₂, respectively. These results suggest that the hypertensive effect of AA may be composed of various actions of the above-mentioned PG and the related substances synthetized from AA in the brain tissues.