The motor innervation of the rat urinary bladder.

1. The post-ganglionic nerves visible in silver-impregnated sections of a normal rat bladder were absent 14 days after both pelvic ganglia had been ablated. After ablation of one ganglion the distribution of nerve trunks in either side of the organ was unchanged. Post-ganglionic axons from either side appear to distribute bilaterally.2. The acetylcholine (ACh) content of the rat bladder was reduced from control by 50% after the post-ganglionic nerves from one ganglion had degenerated. However, the ACh content in the two halves of the bladder sectioned along the mid line was the same after one nerve had degenerated.3. Motor responses of bladder preparations elicited during stimulation of both pelvic nerves were compared with responses elicited when each nerve was stimulated separately. In three-quarters of the animals the sum of the individual responses exceeded the response to combined nerve stimulation by no more than 20%. The functional overlap between the two groups of motor nerves to the bladder was therefore no greater than this amount in most animals.4. Motor responses of normally innervated bladder preparations elicited in vitro by transmural stimulation were compared with responses elicited after the post-ganglionic innervation from one side had degenerated. The mean response of bladders with half their innervation was 50-65% of the mean response of bladders normally innervated. The functional overlap by the two groups of nerves was found to be no greater than 15%.