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Relaxant effects of potassium‐channel openers on normal and hyper‐reflexic detrusor muscle
Author(s) -
MARTIN S.W.,
RADLEY S.C.,
CHESSWILLIAMS R.,
KORSTANJE C.,
CHAPPLE C.R.
Publication year - 1997
Publication title -
british journal of urology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 0007-1331
DOI - 10.1046/j.1464-410x.1997.00257.x
Subject(s) - carbachol , detrusor instability , tetrodotoxin , chemistry , stimulation , detrusor muscle , atropine , endocrinology , medicine , potassium channel , potassium , potency , urinary bladder , urinary system , biochemistry , in vitro , organic chemistry
Objective To compare the effects of the potassium‐channel openers, levcromakalim and YM934, in isolated human detrusor muscle from normal and hyper‐reflexic bladders. Materials and methods Strips of human detrusor muscle from normal and hyper‐reflexic bladder were pre‐contracted with carbachol and the potassium‐channel openers (0.1–0.3 μmol/L) were added cumulatively to the organ baths. Other strips were field‐stimulated at frequencies producing 25% and 75% of the maximum response to field stimulation. Contractions could be abolished by atropine (10 μmol/L) and tetrodotoxin (1 μmol/L). Results The hyper‐reflexic bladder was significantly more sensitive to carbachol than the normal bladder but the maximum response was significantly lower in the hyper‐reflexic tissue. There was no significant difference between the potency of the potassium‐channel openers in normal and hyper‐reflexic detrusor muscle. Hyper‐reflexic bladder was significantly more sensitive to electrical field stimulation than was normal bladder; maximum responses to field stimulation were not significantly different. Concentration‐response curves for the potassium‐channel openers were displaced to the left in hyper‐reflexic bladder at both 25% and 75% maximum frequencies; however, only with levcromakalim at 75% of the maximum frequency was the shift significant. Conclusion The greater sensitivity of hyper‐reflexic bladder to carbachol and field stimulation supports existing evidence for post‐junctional supersensitivity in detrusor instability. The results of this study also suggest that there are no appreciable changes in K ATP channel function in the unstable bladder.