QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: jpet.107.131011v1 324/3/1011    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hu, X.-Q. Articles by Peoples, R. W. Search for Related Content PubMed PubMed Citation Articles by Hu, X.-Q. Articles by Peoples, R. W.

NEUROPHARMACOLOGY

Arginine 246 of the Pretransmembrane Domain 1 Region Alters 2,2,2-Trichloroethanol Action in the 5-Hydroxytryptamine_3A Receptor

Department of Biomedical Sciences, College of Health Sciences, Marquette University, Milwaukee, Wisconsin

Ligand-gated ion channels participate in synaptic transmission, and they are involved in neurotransmitter release. The functions of the channels are regulated by a variety of modulators. The interaction of 2,2,2-trichloroethanol, the active hypnotic metabolite of chloral hydrate, with the 5-hydroxytryptamine (5-HT) (serotonin) type 3 receptor results in a positive allosteric modulation. We have demonstrated previously that arginine 246 (R246) located in the pretransmembrane domain 1 is critical for coupling agonist binding to gating. In this study, we examined the role of R246 in the action of trichloroethanol with a combination of mutagenesis and whole-cell patch-clamp techniques. The R246A mutation converted the partial agonist dopamine into a full agonist at the 5-HT_3A receptor, and it facilitated activation of the mutant receptor by dopamine, suggesting an enhanced gating process due to the mutation. The positive modulation of the 5-HT_3A receptor by trichloroethanol was dramatically reduced by the R246A mutation. Trichloroethanol had little agonist activity in the wild-type receptor (<1% of maximal 5-HT response). However, the R246A mutation significantly increased the direct activation of the receptor by trichloroethanol in the absence of agonist (10% of maximal 5-HT response). The current activated by trichloroethanol could be blocked by the competitive 5-HT₃ receptor antagonist tropanyl 3,5-dichlorobenzoate (MDL 72222), and it had a similar reversal potential to those of current activated by 5-HT. In addition, predesensitization of the mutant receptor by trichloroethanol prevented 5-HT from activating the receptor. These data suggest that R246 is a crucial site for mediating the actions of both agonists and modulators.

Address correspondence to: Dr. Robert W. Peoples, Department of Biomedical Sciences, Marquette University, P.O. Box 1881, Milwaukee, WI 53201-1881. E-mail: robert.peoples{at}marquette.edu