Abstract
1 (+)-Lysergic acid diethylamide (LSD) mimicked 5-hydroxytryptamine (5-HT) in its ability to stimulate fluid secretion, to change transepithelial and intracellular potentials as well as to increase the cyclic 3′,5′-adenosine monophosphate (cyclic AMP) concentrations of isolated salivary glands of Calliphora. 2 Unlike 5-HT, LSD disengages slowly from the receptor and fluid secretion continues despite repeated washing. 3 Both 5-HT and tryptamine prevented LSD from acting on the glands. 4 LSD bound to the receptor was slowly displaced when glands were treated with agonists (tryptamine) or antagonists (gramine). 5 The property of LSD which permits it to function as an agonist despite remaining tightly bound to the receptor is discussed as a possible basis for its profound effects within the central nervous system.