Blockage of 5HT2C serotonin receptors by fluoxetine (Prozac).
Fluoxetine (Prozac) inhibited the membrane currents elicited by serotonin (5-hydroxytryptamine; 5HT) in Xenopus oocytes expressing either cloned 5HT2C receptors or 5HT receptors encoded by rat cortex mRNA. Responses of 5HT2C receptors, elicited by nM concentrations of 5HT, were rapidly and reversibly blocked by micromolar concentrations of fluoxetine. For responses elicited by 1 microM 5HT, the IC50 of fluoxetine inhibition was approximately 20 microM. In accord with the electrophysiological results, fluoxetine inhibited the binding of [3H]5HT to 5HT2C receptors expressed in HeLa cells (Ki approximately 65-97 nM), and the binding to 5HT receptors in rat cortex membranes was also inhibited but less efficiently (Ki approximately 56 microM). Our results show that fluoxetine is a competitive and reversible antagonist of 5HT2C receptors and suggest that some therapeutic effects of fluoxetine may involve blockage of 5HT receptors, in addition to its known blockage of 5HT transporters. Similar work may help to design more selective compounds for use in the treatment of brain disorders.
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Department of Psychobiology, University of California, Irvine 92697-4550, USA.
Miledi
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D000805:Angiotensin III / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005473:Fluoxetine / Q000494:pharmacology*; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000378:metabolism; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D044405:Receptor, Serotonin, 5-HT2C; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D014162:Transfection / Q000235:genetics; D014981:Xenopus
D000805:Angiotensin III; D002352:Carrier Proteins; D005473:Fluoxetine; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D044405:Receptor, Serotonin, 5-HT2C; D011985:Receptors, Serotonin; D012701:Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors; C493230:SLC6A4 protein, human; C493232:Slc6a4 protein, rat