Effect of partial outlet obstruction on choline acetyltransferase activity in the rat and rabbit

Partial outlet obstruction of the rabbit bladder induces a rapid and significant increase in bladder mass. This increase in mass is associated with a variety of specific contractile dysfunctions, characterized by a marked decrease in the response to field stimulation (acting through the release of neurogenic transmitters). There is histological evidence indicating that the decrease in the contractile response of isolated strips of rabbit urinary bladder to field stimulation is associated with a degeneration of synaptic membranes within the bladder detrusor (neuropathy). In the current experiments, the effect of partial outlet obstruction in rabbit and rat urinary bladders on choline acetyltransferase activity (ChAT) were determined and correlated with both the level of bladder hypertrophy (increase in mass) and the contractile response to field stimulation. The results can be summarized as follows: In the rabbit, partial outlet obstruction induced a rapid 5‐fold increase in bladder mass over the 7 day period of study. This increase in mass was associated with a decrease in the contractile response of isolated strips of bladder body and base to field stimulation and a decrease in ChAT activity. Interestingly, the rabbit bladder base showed a significantly higher ChAT activity than the bladder body, although the contractile response to muscarinic stimulation was significantly greater in the bladder body than in the base. In the rat, partial outlet obstruction induced a mild 2‐fold increase in bladder mass. No change in ChAT activity was observed in the obstructed bladder. Consistent with this finding, there was no dysfunction in the response to field stimulation in the obstructed rat bladder.