Muscarinic stimulation of the rat isolated whole bladder: pathophysiological models of detrusor overactivity.

1 Hypotheses as to the pathophysiological basis of bladder detrusor muscle overactivity (DO) have identified both central nervous and peripheral mechanisms as likely contributory factors. In this paper, we describe peripheral autonomous bladder activity in two animal models of DO and discuss how the differences observed between the two models support the likelihood that clinical DO has a multifactorial basis. 2 A total of 12 adult female Sprague-Dawley rats underwent obstruction or sham operation for 1 or 4 weeks. Six adult female spontaneously hypertensive rats (SHR) were compared with normal Wistar controls. Bladders were microsurgically removed and mounted in whole organ tissue baths. Recordings of intravesical pressure in response to the muscarinic receptor agonist arecaidine were performed under standardized conditions. 3 In the partially obstructed rat bladder, the amplitude of pressure fluctuations elicited by the muscarinic agonist arecaidine was significantly increased compared with sham-operated animals. The tonic component of the response was no different for the two groups. No difference from controls was apparent in the SHR. 4 We conclude that alterations in autonomous bladder activity in the obstructed rat model suggest that peripheral functional changes contribute to the pathophysiological abnormality. In contrast, the fundamental abnormality in the SHR appears to be at a more central level. The observations support the supposition that lesions at widely separate sites can give rise to apparently similar abnormalities of lower urinary tract function.