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Journal of Biomedicine and Biotechnology
Volume 2004 (2004), Issue 1, Pages 10-15
Research article

Patch Clamp Study of Serotonin-Gated Currents via 5-HT Type 3 Receptors by Using a Novel Approach SHAM for Receptor Channel Scanning

1Biology Department, Faculty of Science, University of UAE, PO Box 17551, Al Ain, United Arab Emirates
2Department of Pharmacology and Physiology, College of Medicine, Drexel University, Philadelphia 19104, PA, USA

Received 22 February 2003; Revised 26 April 2003; Accepted 3 June 2003

Copyright © 2004 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We studied 5-hydroxy tryptamine type 3 (5-HT3) receptors transfected in tsA-201 cell line to examine serotonin-induced whole cell currents. Using the site-directed mutagenesis technique, we individually mutated each residue in the membrane-spanning M2 segment to histidine. A high proportion of tsA-201 cells cotransfected with the cDNAs of 5-HT3R and CD8 produced large amplitude responses (0.5–7.0 nA) to serotonin. The dose-response curve of wild-type (WT) receptor ranging from 0.5 to 500 μmole increases its Kd values, and Imax of 5-HT3R falls at low external pH as if protonation of an acid group is enough to block the channel. Lysine at position 281, a basic residue, is more susceptible to acidification-induced blockade of the 5-HT3R channel. Dose-response curves of K281S (replacing lysine at the 281 position with serine) at different pH are not significantly modulated, and histidine substitutions at the three consecutive positions 293, 294, and 296 eliminate the pH block of the channel.