EVIDENCE FOR THE ACTION OF d-LYSERGIC ACID DIETHYLAMIDE, MESCALINE AND BUFOTENINE ON 5-HYDROXYTRYPTAMINE RECEPTORS IN UMBILICAL VASCULATURE

¹ Department of Pharmacology and The Anesthesia Research Center, School of Medicine, University of Washington, Seattle, Washington

The contractions produced to 5-hydroxytryptamine, d-lysergic acid diethylamide (LSD), mescaline and bufotenine were studied on isolated helically cut sheep umbilical arteries. Phenoxybenzamine antagonized contractions to all four of the above agonists. When the tissues were incubated with 5-hydroxytryptamine (1.7 x 10^-4 M) before and during exposure to phenoxybenzamine, the degree of block of the contractions to 5-hydroxytryptamine produced by phenoxybenzamine was less, i.e., the 5-hydroxytryptamine protected its own receptors against attack by the phenoxybenzamine. However, neither histamine, acetylcholine, norepinephrine nor angiotensin protected 5-hydroxytryptamine receptors. 5-Hydroxytryptamine did not protect norepinephrine or acetyhchohine receptors. 5-Hydroxytryptamine protected receptors mediating contractions for mescaline, bufotenine and LSD against block by the phenoxybenzamine. Also, mescaline and bufotenine protected 5-hydroxytryptamine receptors. Cross-protection experiments between LSD and 5-hydroxytryptamine could not be studied because of the prolonged time needed for the tissue to return to base line, even with repeated washes, when exposed to LSD. Mescaline protected receptors mediating contractions for LSD. The present study is in agreement with our previous experiments (Dyer, D.C. and Gant, D.W.: J. Pharmacol. Exp. Ther. 184: 366-375, 1973) in which LSD, mescaline and bufotenine were found to contract umbilical vasculature via 5-hydroxytryptamine receptors.