Action of Depressor-I, a hypotensive phospholipid from bovine brain, on systemic and arterial blood pressures of various species.

Abstract

Effects of Depressor-I (D-I), a new hypotensive phospholipid obtained from bovine brain lipid fraction, on systemic arterial blood pressure were investigated. The hypotensive antivity of D-I in urethane anesthetized rats was dose dependent and tachyphylaxis and/or sensitization were not observed. Increments of the respiration and the heart rate were observed with sharp falls in blood pressures following i.v. administration of D-I in simultaneous recordings in anesthetized rats. D-I elicited hypotension in all species of animals examined, and the sensitivities to D-I were much the same. There were 2 types in patterns of duration on responses, and the durations were dose dependent. D-I exhibited depressor-responses in conscious rats, though responses were much smaller compared to those in anesthetized rats. In a comparison of anesthetic agents in rats, the highest hypotensive activity of D-I was observed with pentobarbital anesthesia,, a moderate response was seen with .alpha.-chloralose and the least response was seen with urethane. In spinal rats or those pretreated with reserpine or antagonists, such as atropine, diphenhydramine, propranolol and hexamethonium, D-I elicited hypotension. Apparently Depressor-I does not elicit the depressor action via the stimulation of the central and the autonomic nervous systems but rather by a direct action on peripheral blood vessels.