THE EFFECT OF RYANODINE ON PERIPHERAL VASCULAR RESISTANCE IN THE ANESTHETIZED CAT. EVIDENCE FOR A CENTRALLY-INDUCED VASOCONSTRICTION

¹ Departments of Pharmacology, Downstate Medical Center, State University of New York, Brooklyn, and Albany Medical College of Union University, Albany, New York

To gain information on the effects of ryanodine on the peripheral circulation of anesthetized animals, blood flow, utilizing a photoelectric drop recording method, was followed in various peripheral vascular beds before and after the administration of ryanodine. In doses of as little as 5 µg/kg, ryanodine induced a definitive increase in the resistance of the vascular beds of the hind-limb, the spleen and tissues of the head and neck. Large doses were required to increase vascular resistance in the kidney. In the bed drained by the superior mesenteric vein vascular resistance was unchanged or decreased. From data obtained on sectioning the sciatic nerve to the experimental limb, on spinal cord-sectioned animals and on carotid-debuffered animals, the conclusion is drawn that the action of ryanodine is mediated through an effect on some area of the brain which participates in the control of the peripheral circulation.