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This Article Full Text Full Text (PDF) All Versions of this Article: 583/2/505    most recent jphysiol.2007.136697v1 Services Email this article to a friend 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 Hashitani, H. Articles by Suzuki, H. Search for Related Content PubMed PubMed Citation Articles by Hashitani, H. Articles by Suzuki, H. Related Collections Cellular

¹ Department of Regulatory Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan

Interstitial cells of Cajal-like cells (ICC-LCs) in the urethra may act as electrical pacemakers of spontaneous contractions. However, their properties in situ and their interaction with neighbouring urethral smooth muscle cells (USMCs) remain to be elucidated. To further explore the physiological role of ICC-LCs, spontaneous changes in [Ca²⁺]_i (Ca²⁺ transients) were visualized in fluo-4 loaded preparations of rabbit urethral smooth muscle. ICC-LCs were sparsely distributed, rather than forming an extensive network. Ca²⁺ transients in ICC-LCs had a lower frequency and a longer half-width than those of USMCs. ICC-LCs often exhibited Ca²⁺ transients synchronously with each other, but did not often show a close temporal relationship with Ca²⁺ transients in USMCs. Nicardipine (1 µM) suppressed Ca²⁺ transients in USMCs but not in ICC-LCs. Ca²⁺ transients in ICC-LCs were abolished by cyclopiazonic acid (10 µM), ryanodine (50 µM) and caffeine (10 mM) or by removing extracellular Ca²⁺, and inhibited by 2-aminoethoxydiphenyl borate (50 µM) and 3-morpholino-sydnonimine (SIN-1; 10 µM), but facilitated by increasing extracellular Ca²⁺ or phenylephrine (1–10 µM). These results indicated that Ca²⁺ transients in urethral ICC-LCs in situ rely on both Ca²⁺ release from intracellular Ca²⁺ stores and Ca²⁺ influx through non-L-type Ca²⁺ channel pathways. ICC-LCs may not act as a coordinated pacemaker electrical network as do ICC in the gastrointestinal (GI) tract. Rather they may randomly increase excitability of USMCs to maintain the tone of urethral smooth muscles.

(Received 17 May 2007; accepted after revision 29 June 2007; first published online 5 July 2007)
Corresponding author H. Hashitani: Department of Regulatory Cell Physiology, Nagoya City University, Graduate School of Medical Sciences, Nagoya 467-8601, Japan. Email: hasitani{at}med.nagoya-cu.ac.jp