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 s ignificant increase in bladder mass. This increase in mass is associat ed with a variety of specific contractile dysfunctions, characterized by a marked decrease in the response to field stimulation (acting thro ugh the release of neurogenic transmitters). There is histological evi dence indicating that the decrease in the contractile response of isol ated strips of rabbit urinary bladder to field stimulation is associat ed with a degeneration of synaptic membranes within the bladder detrus or (neuropathy). In the current experiments, the effect of partial out let obstruction in rabbit and rat urinary bladders on choline acetyltr ansferase activity (ChAT) were determined and correlated with both the level of bladder hypertrophy (increase in mass) and the contractile r esponse to field stimulation. The results can be summarized as follows : In the rabbit, partial outlet obstruction induced a rapid 5-fold inc rease in bladder mass over the 7 day period of study. This increase in mass was associated with a decrease in the contractile response of is olated strips of bladder body and base to field stimulation and a decr ease in ChAT activity. Interestingly, the rabbit bladder base showed a significantly higher ChAT activity than the bladder body, although th e contractile response to muscarinic stimulation was significantly gre ater 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 wi th this finding, there was no dysfunction in the response to field sti mulation in the obstructed rat bladder.