title: Ethanol and trichloroethanol alter gating of 5-HT3 receptor-channels in NCB-20 neuroblastoma cells.
abstract: Alcohol potentiation of 5-HT3 receptors was examined in NCB-20 neuroblastoma cells using whole-cell patch-clamp electrophysiological techniques. Activation of the receptor with the weak partial agonist dopamine (DA) was used to examine alcohol effects under conditions of full agonist occupancy, but low probability of channel opening. Dopamine activation of the receptor increased in a concentration-dependent manner (EC50=0.28 mM), and on average maximal responses to DA were 8.0+/-0.8% of the maximal response to 5-HT. Ethanol (EtOH) and trichloroethanol (TCEt) potentiated DA-activated ion current mediated by 5-HT3 receptors. Potentiation of responses to a maximally effective dopamine concentration averaged 52.0+/-8.0% for EtOH and 567+/-43% for TCEt, which was comparable to the potentiation observed when receptors were activated by a low concentration of 5-HT. The alcohols increased both the potency and efficacy with which dopamine activated the receptor. The observation that alcohols increase the maximal efficacy of dopamine activation of the receptor indicates that one action of alcohols on the 5-HT3 receptor is to increase the probability of channel opening independent of any effect on agonist affinity.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA. david.lovinger@mcmail.vanderbilt.edu
authors.forename: D M
authors.initials: DM
authors.lastname: Lovinger
authors.forename: K W
authors.initials: KW
authors.lastname: Sung
authors.forename: Q
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D004298:Dopamine / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D005023:Ethylene Chlorohydrin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015640:Ion Channel Gating; D018408:Patch-Clamp Techniques; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D044406:Receptors, Serotonin, 5-HT3; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D017366:Serotonin Receptor Agonists; D000431:Ethanol; D005023:Ethylene Chlorohydrin; C005849:2,2,2-trichloroethanol; D004298:Dopamine