HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 292/5/R2100    most recent 00779.2006v1 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 HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Ng, Y.-K. Articles by Wu, H.-Y. Search for Related Content PubMed PubMed Citation Articles by Ng, Y.-K. Articles by Wu, H.-Y.

WATER AND ELECTROLYTE HOMEOSTASIS

Smooth muscle and neural mechanisms contributing to the downregulation of neonatal rat spontaneous bladder contractions during postnatal development

¹Department of Surgery, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong; ²Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania; and ³Department of Pediatric Urology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania

Submitted 8 November 2006 ; accepted in final form 16 January 2007

Spontaneous bladder contractions (SBCs) in the neonatal rat urinary bladder change from a high-amplitude, low-frequency pattern to a low-amplitude, high-frequency pattern during the first 6 wk of life. Understanding the mechanism of this developmental change may provide insights into the causes of bladder overactivity in adults. In vitro whole bladder preparations from Sprague-Dawley rats were used to study the modulation of SBCs by calcium-activated potassium channels (K_Ca) and electrical field stimulation from 3 days to 6 wk of life. SBCs in 3-day-old bladders were unmasked by treatment with iberiotoxin (100 nM), an inhibitor of large conductance K_Ca (BK) channels, or apamin (100 nM), an inhibitor of small conductance K_Ca (SK) channels. Iberiotoxin significantly increased the magnitude of SBCs at 2–3 wk, whereas apamin was only effective at 6 wk. In 1–2 wk bladders, exposure to room temperature Krebs solution decreased SBCs. This decrease was reversed by activating intramural nerves with electrical field stimulation. The effect of electrical field stimulation was inhibited by atropine (1 µM), suramin (10 µM), or pretreatment with tetrodotoxin (1 µM) but was not reversed by tetrodotoxin applied after electrical field stimulation. BK- mRNA increased threefold, and BK- protein increased fivefold from 3 days to 6 wk. These data suggest that BK channels play an important role in the regulation of SBCs in the neonatal bladder and that both increased BK channel activity, as well as changes in smooth muscle sensitivity to locally released neurotransmitters contribute to the downregulation of SBCs during early postnatal development.

large-conductance K_Ca channel; small-conductance K_Ca channel; cholinergic; purinergic

This article has been cited by other articles:

				M. B. Klinger, A. Dattilio, and M. A. Vizzard Expression of cyclooxygenase-2 in urinary bladder in rats with cyclophosphamide-induced cystitis Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2007; 293(2): R677 - R685. [Abstract] [Full Text] [PDF]