Effects of pelvic nerve neurectomy and estrogen on the M2 muscarinic receptor of the urinary bladder

Background: Normal physiological voiding, as well as generation of abnormal bladder contractions in the diseased state, is critically dependent on acetylcholine-induced stimulation of contractile muscarinic receptors on the detrusor muscle of the urinary bladder. This study investigated the effect of pelvic nerve neurectomy and estrogen treatment on the M2 muscarinic receptors of urinary bladder. Methods: We studied the muscarinic cholinergic receptor density in the urinary bladder of castrated female rats following four weeks of estrogen treatment and/or pelvic nerve neurectomy. We used immunohistochemistry to detect the expression of M2 receptors on the smooth muscle cells of urinary bladder. Results: When compared to a sham-operated group, the M2 receptors in the urinary bladders of rats that had undergone bilateral pelvic nerve neurectomy and estrogen treatment, showed no significant change. However, the M2 receptors decreased significantly in the urinary bladders of rats that had undergone simultaneous estrogen treatment and bilateral pelvic nerve neurectomy, when compared to the other groups (p < 0.05). Conclusion: Pelvic nerve denervation has a synergetic effect on the estrogen-induced down regulation of M2 receptor immunoreactive cells in the urinary bladder.