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This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/F645    most recent 00526.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science 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 Johnston, L. Articles by McCloskey, K. D. Search for Related Content PubMed PubMed Citation Articles by Johnston, L. Articles by McCloskey, K. D.

Cholinergic-induced Ca²⁺ signaling in interstitial cells of Cajal from the guinea pig bladder

¹Physiology, Division of Basic Medical Sciences, Medical Biology Centre, Belfast, Northern Ireland; and ²Centre for Biophotonics, University of Strathclyde, Glasgow, Scotland, United Kingdom

Submitted 7 November 2007 ; accepted in final form 28 December 2007

Acetylcholine released from parasympathetic excitatory nerves activates contraction in detrusor smooth muscle. Immunohistochemical labeling of guinea pig detrusor with anti-c-Kit and anti-VAChT demonstrated a close structural relationship between interstitial cells of Cajal (ICC) and cholinergic nerves. The ability of guinea pig bladder detrusor ICC to respond to the acetylcholine analog, carbachol, was investigated in enzymatically dissociated cells, loaded with the Ca²⁺ indicator fluo 4AM. ICC fired Ca²⁺ transients in response to stimulation by carbachol (1/10 µM). Their pharmacology was consistent with carbachol-induced contractions in strips of detrusor which were inhibited by 4-DAMP (1 µM), an M₃ receptor antagonist, but not by the M₂ receptor antagonist methoctramine (1 µM). The source of Ca²⁺ underlying the carbachol transients in isolated ICC was investigated using agents to interfere with influx or release from intracellular stores. Nifedipine (1 µM) or Ni²⁺ (30–100 µM) to block Ca²⁺ channels or the removal of external Ca²⁺ reduced the amplitude of the carbachol transients. Application of ryanodine (30 µM) or tetracaine (100 µM) abolished the transients. The phospholipase C inhibitor, U-73122 (2.5 µM), significantly reduced the responses. 2-Aminoethoxydiethylborate (30 µM) caused a significant reduction and Xestospongin C (1 µM) was more effective, almost abolishing the responses. Intact in situ preparations of guinea pig bladder loaded with a Ca²⁺ indicator showed distinctively different patterns of spontaneous Ca²⁺ events in smooth muscle cells and ICC. Both cell types responded to carbachol by an increase in frequency of these events. In conclusion, guinea pig bladder detrusor ICC, both as isolated cells and within whole tissue preparations, respond to cholinergic stimulation by firing Ca²⁺ transients.

confocal microscopy; c-Kit