CHARACTERIZATION OF [H-3] LSD BINDING TO A SEROTONIN-SENSITIVE SITE IN HONEYBEE (APIS-MELLIFERA) BRAIN

The binding of [H-3]lysergic acid diethylamide ([H-3]LSD) to a putative serotonin receptor site (S-site) in membrane preparations of honeybee brain was analyzed. All experiments were performed in the presence of 10 mu M dopamine to inhibit [H-3]LSD binding to an additional site, which is dopamine-sensitive (D-site), [H-3]LSD binds reversibly to the S-site with a K-D value of 0.89 nM. The maximal concentration of binding sites is 790 fmol/mg protein, Serotonin, lisuride, methysergide, 5-methoxytryptamine and tryptamine are the most potent displacers of S-site binding, The displacement efficacy of several other potential serotonin receptor agonists and antagonists was analyzed. Addition of the stable GTP analogue GTP gamma S or high sodium concentrations reduced specific [H-3]LSD binding to the putative serotonin receptor binding site.