THE EFFECTS OF RICIN ON THE SYMPATHETIC VASCULAR NEUROEFFECTOR SYSTEMOF THE RABBIT

Ricin is a toxic lectin that inhibits protein synthesis. Because ricin decreases arterial pressure and causes cardiovascular collapse, its e ffects on the vascular neuroeffector system were investigated. Rabbits were given either of two doses of ricin, and then norepinephrine (NE) release from aorta to transmural stimulation, NE uptake into aorta, N E content of aorta, monoamine oxidase activity, and catechol-O-methyl transferase activity in aorta were determined 18 hours, 4 days or 7 da ys later. Norepinephrine uptake and enzyme activities in the aorta wer e not altered by ricin administration. Norepinephrine release and cont ent of aorta were increased at most time periods following ricin admin istration, significantly so for NE content at 4 days and for release a t 18 hours following the lower dose of ricin. We conclude that the mec hanisms involved in the release of NE from sympathetic nerves in the v asculature are not impaired by ricin administration, but rather show c hanges that indicate increased compensatory activity.