Russell A Morton1,2, Daniel T Baptista-Hon3, Tim G Hales2,3, David M Lovinger1,2. 1. Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, MD, USA. 2. Department of Pharmacology and Physiology, George Washington University, Washington, DC, USA. 3. Institute of Academic Anaesthesia, Division of Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.
Abstract
BACKGROUND AND PURPOSE: The 5-HT3 receptor is a member of the pentameric ligand-gated ion channel family and is pharmacologically targeted to treat irritable bowel syndrome and nausea/emesis. Furthermore, many antidepressants elevate extracellular concentrations of 5-HT. This study investigates the functional consequences of exposure of recombinant 5-HT3 A receptors to agonists and antagonists. EXPERIMENTAL APPROACH: We used HEK cells stably expressing recombinant 5-HT3 A receptors and the ND7/23 (mouse neuroblastoma/dorsal root ganglion hybrid) cell line, which expresses endogenous 5-HT3 receptors. Surface expression of recombinant 5-HT3 A receptors, modified to contain the bungarotoxin (BTX) binding sequence, was quantified using fluorescence microscopy to image BTX-conjugated fluorophores. Whole cell voltage-clamp electrophysiology was used to measure the density of current mediated by 5-HT3 A receptors. KEY RESULTS: 5-HT3 A receptors were up-regulated by the prolonged presence of agonists (5-HT and m-chlorophenylbiguanide) and antagonists (MDL-72222 and morphine). The up-regulation of 5-HT3 A receptors by 5-HT and MDL-72222 was time- and concentration-dependent but was independent of newly translated receptors. The phenomenon was observed for recombinant rodent and human 5-HT3 A receptors and for endogenous 5-HT3 receptors in neuronal ND7/23 cells. CONCLUSIONS AND IMPLICATIONS: Up-regulation of 5-HT3 A receptors, following exposure to either agonists or antagonists suggests that this phenomenon may occur in response to different therapeutic agents. Medications that elevate 5-HT levels, such as the antidepressant inhibitors of 5-HT reuptake and antiemetic inhibitors of 5-HT3 receptor function, may both raise receptor expression. However, this will require further investigation in vivo.
BACKGROUND AND PURPOSE: The 5-HT3 receptor is a member of the pentameric ligand-gated ion channel family and is pharmacologically targeted to treat irritable bowel syndrome and nausea/emesis. Furthermore, many antidepressants elevate extracellular concentrations of 5-HT. This study investigates the functional consequences of exposure of recombinant 5-HT3 A receptors to agonists and antagonists. EXPERIMENTAL APPROACH: We used HEK cells stably expressing recombinant 5-HT3 A receptors and the ND7/23 (mouseneuroblastoma/dorsal root ganglion hybrid) cell line, which expresses endogenous 5-HT3 receptors. Surface expression of recombinant 5-HT3 A receptors, modified to contain the bungarotoxin (BTX) binding sequence, was quantified using fluorescence microscopy to image BTX-conjugated fluorophores. Whole cell voltage-clamp electrophysiology was used to measure the density of current mediated by 5-HT3 A receptors. KEY RESULTS:5-HT3 A receptors were up-regulated by the prolonged presence of agonists (5-HT and m-chlorophenylbiguanide) and antagonists (MDL-72222 and morphine). The up-regulation of 5-HT3 A receptors by 5-HT and MDL-72222 was time- and concentration-dependent but was independent of newly translated receptors. The phenomenon was observed for recombinant rodent and human5-HT3 A receptors and for endogenous 5-HT3 receptors in neuronal ND7/23 cells. CONCLUSIONS AND IMPLICATIONS: Up-regulation of 5-HT3 A receptors, following exposure to either agonists or antagonists suggests that this phenomenon may occur in response to different therapeutic agents. Medications that elevate 5-HT levels, such as the antidepressant inhibitors of 5-HT reuptake and antiemetic inhibitors of 5-HT3 receptor function, may both raise receptor expression. However, this will require further investigation in vivo.
Authors: Russell A Morton; Guoxiang Luo; Margaret I Davis; Tim G Hales; David M Lovinger Journal: Mol Cell Neurosci Date: 2011-02-19 Impact factor: 4.314
Authors: Henry A Lester; Cheng Xiao; Rahul Srinivasan; Cagdas D Son; Julie Miwa; Rigo Pantoja; Matthew R Banghart; Dennis A Dougherty; Alison M Goate; Jen C Wang Journal: AAPS J Date: 2009-03-12 Impact factor: 4.009
Authors: Mitesh Sanghvi; Ayman K Hamouda; Margaret I Davis; Russell A Morton; Shouryadeep Srivastava; Akash Pandhare; Phaneendra K Duddempudi; Tina K Machu; David M Lovinger; Jonathan B Cohen; Michael P Blanton Journal: Biochemistry Date: 2009-10-06 Impact factor: 3.162