The Journal of Neuroscience, June 16, 2004, 24(24):5537-5548; doi:10.1523/JNEUROSCI.5658-03.2004
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Cellular/Molecular
Uropathic Observations in Mice Expressing a Constitutively Active Point Mutation in the 5-HT3A Receptor Subunit
Anindya Bhattacharya,1
Hong Dang,2
Quan-Ming Zhu,1
Birthe Schnegelsberg,1
Nora Rozengurt,3
Gary Cain,1
Rachelle Prantil,4
David A. Vorp,4
Nicholas Guy,5
David Julius,5
Anthony P. D. W. Ford,1
Henry A. Lester,2 and
Debra A. Cockayne1
1Roche Pharmaceuticals, Palo Alto, California 94304, 2Caltech, Pasadena, California 91125, 3Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California 90095, 4Departments of Surgery and Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, and 5Department of Cell and Molecular Pharmacology, University of California San Francisco, San Francisco, California 94143
Mutant mice with a hypersensitive serotonin (5-HT)3A receptor were generated through targeted exon replacement. A valine to serine mutation (V13'S) in the channel-lining M2 domain of the 5-HT3A receptor subunit rendered the 5-HT3 receptor
70-fold more sensitive to serotonin and produced constitutive activity when combined with the 5-HT3B subunit. Mice homozygous for the mutant allele (5-HT3Avs/vs) had decreased levels of 5-HT3A mRNA. Measurements on sympathetic ganglion cells in these mice showed that whole-cell serotonin responses were reduced, and that the remaining 5-HT3 receptors were hypersensitive. Male 5-HT3Avs/vs mice died at 2-3 months of age, and heterozygous (5-HT3Avs/+) males and homozygous mutant females died at 4-6 months of age from an obstructive uropathy. Both male and female 5-HT3A mutant mice had urinary bladder mucosal and smooth muscle hyperplasia and hypertrophy, whereas male mutant mice had additional prostatic smooth muscle and urethral hyperplasia. 5-HT3A mutant mice had marked voiding dysfunction characterized by a loss of micturition contractions with overflow incontinence. Detrusor strips from 5-HT3Avs/vs mice failed to contract to neurogenic stimulation, despite overall normal responses to a cholinergic agonist, suggestive of altered neuronal signaling in mutant mouse bladders. Consistent with this hypothesis, decreased nerve fiber immunoreactivity was observed in the urinary bladders of 5-HT3Avs/vs compared with 5-HT3A wild-type (5-HT3A+/+) mice. These data suggest that persistent activation of the hypersensitive and constitutively active 5-HT3A receptor in vivo may lead to excitotoxic neuronal cell death and functional changes in the urinary bladder, resulting in bladder hyperdistension, urinary retention, and overflow incontinence.
Key words: 5-HT3; mouse; knock-in mutation; bladder; hypertrophy; afferent innervation
Received Dec 22, 2003;
revised March 18, 2004;
accepted April 22, 2004.
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