Effect of estrogen on bladder nociception in rats.
OBJECTIVE
We assessed the effect of ovariectomy and estrogen replacement on nociceptive responses to bladder distention in a rat model.


METHODS
Female Sprague-Dawley rats (Harlan) underwent ovariectomy or sham surgery. Visceromotor responses (abdominal contractions) to bladder distention were determined 3 to 4 weeks later under isoflurane anesthesia. In rat subsets estrogen was chronically replaced with a subcutaneous estrogen pellet vs a placebo pellet or acutely replaced by subcutaneous injection 24 hours before testing. Effects of estrogen withdrawal were examined in another group of rats by implanting a pellet and explanting the pellet 24 hours before testing. Uterine weight was measured to assess the estrogen dose.


RESULTS
Visceromotor responses to bladder distention were significantly less vigorous in ovariectomized rats vs controls. Acute estrogen replacement increased visceromotor responses in these rats but chronic estrogen replacement did not. Sudden chronic estrogen withdrawal resulted in increased visceromotor responses. Uterine weight was consistent with the physiological estrogen dose.


CONCLUSIONS
Estrogen alone was not sufficient to produce increased nociceptive responses but an acute decrease in estrogen resulted in increased visceromotor responses. These data suggest that the pronociceptive effects of estrogen may be due to a mismatch between peripheral vs central and/or genomic vs nongenomic effects of the hormone, which occur during rapidly decreasing estrogen levels.
Robbins
Meredith T
MT
Division of Pain Treatment, Department of Anesthesiology and Division of Behavioral Neuroscience, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Mebane
Hannah
H
Ball
Chelsea L
CL
Shaffer
Amber D
AD
Ness
Timothy J
TJ
D000818:Animals; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology*; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology*
D004967:Estrogens