Mechanisms of ligand-induced desensitization of the 5-hydroxytryptamine (2A) receptor

ABSTRACT We have examined the cellular processes underlying the desensitization of the 5-hydroxytryptamine (5-HT) 2A receptor induced by agonist or antagonist exposure. Treatment of C6 glioma cells with either 5-HT or the 5-HT 2A receptor antagonist ketanserin resulted in an attenuation in 5-HT 2A receptor function, specifically the accumulation of inositol phosphates stimulated by the partial agonist quipazine. 5-HT-induced desensitization of the 5-HT 2A receptor involved receptor internalization through a clathrin-and dynamin-dependent process because it was prevented by concanavalin A, monodansylcadaverine, and by expression of the dominant negative mutants ␤-arrestin (319 -418) and dynamin K44A. Although short-term (i.e., 10 min) 5-HT and ketanserin exposure resulted in the same degree of desensitization, ketanserin-induced desensitization was not prevented by these agents and did not involve receptor internalization. In contrast, prolonged ketanserin exposure (i.e., 2 h) resulted in 5-HT 2A receptor internalization through a clathrinand dynamin-dependent process, as was observed after agonist treatment. Inhibitors of protein kinase C or calcium-calmodulin kinase II did not attenuate or prevent 5-HT-induced desensitization of the receptor. 5-HT 2A receptor desensitization induced by 5-HT and prolonged ketanserin treatment, but not by short-term ketanserin treatment, was prevented by the expression of the dominant negative mutant of G protein-coupled receptor kinase (GRK)2, GRK2-K220R, and by an anti-GRK2/3 antibody. Our data indicate a dual mechanism of early and late desensitization by the antagonist ketanserin. Short-term ketanserin treatment reduced the specific binding of the agonist radioligand Desensitization of G protein-coupled receptors occurs during agonist exposure, often in a matter of minutes. Mechanisms underlying the desensitization of many G proteincoupled receptors have been elucidated in part by using the ␤-adrenergic receptor as a prototype The 5-hydroxytryptamine (5-HT) 2A receptor has been implicated in the mechanism of action of many psychoactive drugs such as hallucinogens, atypical neuroleptics, and antidepressants. The regulation of the 5-HT 2A receptor, however, does not appear to follow the pattern established for many other G protein-coupled receptors. Repeated administration of agonists Given the interest in the role of the 5-HT 2A receptor in the action of many psychoactive drugs and the apparent anomalous regulation of 5-HT 2A receptors by antagonists, including atypical neuroleptics and many antidepressant drug

Neurotrophic Factor Signaling in Alcoholism

This article presents the proceedings of a symposium presented at the meeting of the International Society for the Biomedical Research on Alcoholism (ISBRA), held in Manheim, Germany, in September 2004. The organizers and chairpersons were Subhash C. Pandey and Toshikazu Saito. The presentations were (1) Ethanol and NMDA receptor coupling to ERK signaling, by L.J. Chandler;(2) Ethanol modulation of CREB: Role in neurogenesis, by Fulton Crews;(3) Serotonin dysfunction and alcohol preference in mice deficient in brain-derived neurotrophic factor (BDNF), by Julie G. Hensler; (4) BDNF gene and related signaling: role in anxiety and alcohol dependence and preference, by Subhash C. Pandey; (5) BDNF and CREB: role in ethanol induced neuronal damage, Wataru Ukai

Chronic intermittent cold stress and serotonin depletion induce deficits of reversal learning in an attentional set-shifting test in rats

This find is registered at Portable Antiquities of the Netherlands with number PAN-0005330

Regulation of 5-HT(1A) receptor-stimulated [(35)S]-GTPγS binding as measured by quantitative autoradiography following chronic agonist administration

1. Because changes 5-HT(1A) receptor number do not occur following repeated agonist treatment, we hypothesized that the basis for 5-HT(1A) receptor desensitization involves changes in receptor-G protein coupling. We measured the effect of repeated agonist administration on 5-HT(1A) receptor-stimulated [(35)S]-GTPγS binding in forebrain areas, (i.e. anterior cingulate cortex, lateral septum, hippocampus, entorhinal cortex), and serotonergic cell body areas, the dorsal and median raphe nuclei. 2. Following treatment of rats with (±)8-OH-DPAT (1 mg kg(−1), s.c.) for 7 or 14 days, 5-HT(1A) receptor-stimulated [(35)S]-GTPγS binding was significantly attenuated in both the dorsal and median raphe nuclei. 3. 5-HT(1A) receptor-stimulated [(35)S]-GTPγS binding was significantly attenuated in the CA(1) region of the hippocampus after 7, but not 14 days of 8-OH-DPAT administration. 5-HT(1A) receptor-stimulated [(35)S]-GTPγS binding was not altered in other forebrain areas examined. 4. The binding of [(3)H]-MPPF to 5-HT(1A) receptor sites was not altered in any brain region examined following repeated agonist administration, suggesting that the observed changes in (±)8-OH-DPAT-stimulated [(35)S]-GTPγS binding were not due to changes in 5-HT(1A) receptor number. 5. Our data indicate that in serotonergic cell body areas the regulation of presynaptic 5-HT(1A) receptor function following repeated agonist administration occurs at the level of receptor-G protein interaction. In forebrain areas, however, the regulation of postsynaptic 5-HT(1A) receptor sensitivity appears not to be at the level of receptor-G protein coupling