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Alpha1 -adrenergic receptors mediate bladder overactivity induced by cold stress in rats with bladder outlet
Takahiro Yamagishi1, Osamu Ishizuka, Tetsuya Imamura
1Department of Urology, Shinshu University School of Medicine, Matsumoto, Japan.
Purpose:
To determine if alpha1 -adrenergic receptors (AR) mediate bladder overactivity induced by cold stress in rats with bladder outlet obstruction (BOO).
Materials And Methods:
The urethras of 10-week-old female Sprague-Dawley rats were ligated to create BOO. After 4 weeks, cystometric investigations were performed at room temperature (RT, 27 ± 2°C) for 20 min. The rats were then given 0.3 mg/kg naftopidil (n = 6) or vehicle (n = 5) intravenously. Five minutes later, they were transferred to low temperature (LT, 4 ± 2°C), and the cystometric patterns were again recorded for 40 min. In BOO rats and in sham-operated rats (n = 8) the expression levels of alpha1A - and alpha1D -AR mRNAs and the presence of alpha1A - and alpha1D -AR immunoreactivity on calcitonin gene-related peptide (CGRP)-positive nerve cells were investigated.
Results:
During LT exposure, the vehicle-treated BOO rats exhibited cold stress-induced bladder overactivity. In the naftopidil-treated rats, the increase of basal pressure and decreases of both voiding interval and bladder capacity induced by LT were significantly reduced compared to the vehicle-treated animals. In the bladders of BOO rats exposed to LT, the expression of alpha1D -AR mRNA was significantly higher than in sham-operated rats, and the immunoreactivity for alpha1D -ARs on the CGRP-positive nerve cells tended to be more pronounced.
Conclusions:
Alpha1 -ARs mediate part of the bladder overactivity induced by cold stress in rats with BOO. Cold stress increases the expression of alpha1D -AR mRNA and the immunoreactivity for alpha1D -ARs on the CGRP-positive nerve cells in BOO rats. Naftopidil partially inhibits the cold stress overactivity, suggesting that it is mediated, at least partially, through alpha1D/1A -ARs.
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