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Spontaneous activity of mouse detrusor smooth muscle and the effects of the urothelium
Author(s) -
Meng En,
Young John S.,
Brading Alison F.
Publication year - 2008
Publication title -
neurourology and urodynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 90
eISSN - 1520-6777
pISSN - 0733-2467
DOI - 10.1002/nau.20456
Subject(s) - urothelium , detrusor muscle , urinary bladder , medicine , inhibitory postsynaptic potential , intracellular , anatomy , chemistry , endocrinology , microbiology and biotechnology , biology
Aims To characterize the detrusor muscle of the mouse urinary bladder in order to understand more precisely spontaneous contractile behavior of this organ. This study examined the spontaneous electrical activity and Ca 2+ dynamics of the detrusor smooth muscle and investigated the role of the urothelium. Materials and Methods Detrusor smooth muscle strips were isolated from mouse bladders. The urothelium was either kept intact or removed. Changes in membrane potential were recorded using sharp electrode intracellular recording. To image Ca 2+ dynamics, tissue strips were exposed to 10 µM Oregon Green 488 BAPTA‐1 AM for 70 min, and then image series were acquired with a laser‐scanning confocal microscope. Results (1) Mouse detrusor smooth muscle cells (SMCs) generate nifedipine‐sensitive spontaneous action potentials (sAPs) at a low frequency (1.3 ± 0.9 min −1 , n = 11) in preparations with intact urothelium. This frequency increased when the urothelium was removed (7 ± 8.3 min −1 , n = 17) ( P < 0.05, Student's t test). (2) Frequent ATP‐mediated spontaneous depolarizations were recorded in all cells. (3) The frequency of whole cell Ca 2+ flashes of detrusor smooth muscle cells was higher in preparations with the urothelium removed (median 1.2 min −1 , n = 7) than in urothelium denuded preparations (median 0.6 min −1 , n = 7) ( P < 0.01, Mann–Whitney U ‐test). Conclusions Spontaneous activity of the mouse detrusor smooth muscles was characterized enabling future comparative work on gene knock‐out strains. Evidence suggesting release of an inhibitory factor by the urothelium was apparent. Neurourol. Urodynam. © 2007 Wiley‐Liss, Inc.