Fig. 3.
Hallucinogenic and nonhallucinogenic agonists differentially desensitize 5-HT2A receptors. A, Schema of the experimental paradigm used to investigate the desensitization of 5-HT2A receptor induced by hallucinogenic and nonhallucinogenic agonists in HEK-293 cells and neurons. B and D, Effect of a 1 h pretreatment with either DOI or LSD or lisuride or ergotamine (1 μm each) upon inositol phosphate production elicited by 5-HT (10 μm) in HEK-293 cells (B) and neurons (D). Data, expressed in % of the 5-HT-elicited response in cells pretreated with vehicle are the means ± S.E. of values obtained in three independent experiments performed on different sets of cultured cells. * p < 0.05 versus vehicle-pretreated cells (ANOVA followed by Dunnett's test). C and E, Effects of the corresponding treatments upon 5-HT-elicited Erk1,2 phosphorylation, assessed by sequential immunoblotting with an antibody against phosphorylated Erk1,2 (Thr202-Tyr204) and an antibody recognizing Erk1,2 independently of their phosphorylation state. Immunoblots representative of three independent experiments are shown. Data, expressed as ratios of phosphorylated to total Erk1,2, represent the means ± S.E. of values obtained in the three independent experiments. * p < 0.05, ** p < 0.01 versus cells pretreated with vehicle.