Cervical vagotomy increased the distal colon distention to urinary bladder inhibitory reflex in male rats.

PURPOSE: Many studies have demonstrated the convergence of vagal inputs into brainstem centers with inputs from the urinary bladder and colon, as well as the convergence of vagal inputs into other centers controlling the urinary bladder and colon reflexes. However, the effect of the vagal inputs on the interaction between the urinary bladder and other pelvic organs has not been studied. In this study, the effect of bilateral cervical vagotomy on the distal colon to urinary bladder reflex was examined.

METHODS: Changes to cystometry parameters in response to increased distal colon distensions (1, 2, and 3 ml) were tested in urethane-anesthetized male rats with or without bilateral cervical vagotomy.

RESULTS: In animals with intact vagus nerves, 1 and 2 ml distal colon distentions had no significant effects on micturition frequency; however, 3 ml distal colon distention significantly decreased the frequency of micturition cycles. Also, 3 ml distal colon distention inhibited micturition cycles in 37.5 % of these animals. On the other hand, following cervical vagotomy, 1 ml distal colon distention was enough to significantly decrease the frequency of micturition cycles and to inhibit the cycles in 75 % of the animals.

CONCLUSION: These results demonstrate the presence of supraspinal inhibitory regulation, via the vagus nerve, over the distal colon to urinary bladder inhibitory reflex.