On the Reversibility of Functional Bladder Changes Induced by Infra Vesical Outflow Obstruction in the Rat

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Abstract
Rats were subjected to infravesical outflow obstruction for six weeks. The bladder function was followed by cystometrical and in vitro investigations and by recordings of micturition pattern before and after removal of the obstruction. Cystometrical investigations showed that outflow obstruction for six weeks induced a bladder instability. Further, in the presence of obstruction the micturition prssure was large as was the bladder capacity and the rats had residual urine. After removal of the obstruction the bladder function rapidly normalized. The bladder instability disappeared within one week, bladder capacity decreased as did the micturition pressure. Moreover, only a minor amount of residual urine was present post-obstruction. In vitro investigation showed that the response to carbachol and to electrical stimulation was similar in normal an obstructed bladders. However, after removal of the obstruction a supersensitivity to carbachol as well as to electrical stimulation had developed. Obstructed bladders showed a markedly decreased response to substance P. The sensitivity to substance P was rapidly enhanced post-obstruction and after four days the response was restored to the control level. The present study shows that the bladder function in rats with infravesical outflow obstruction rapidly normalized after removal of the obstruction. the disapperance of the bladder instability despite the developed supersensitivity to muscarinic receptor stimulation supports the opionion that the bladder instability is not of muscarinic origin.