Effects of vesical distention on parasympathetic outflow to the colon of dogs

The vesico-colonic reflex transmitted via the pelvic nerve was studied in dogs and it was found that the reflex consists of four elemental components. 1. Vesical distention produced an inhibition of rectal parasympathetic outflow without eliciting any vesical parasympathetic outflow in decerebrated and spinal dogs. 2. An afterdischarge usually followed the inhbition. These results show that the sacral defecation reflex center is inhibited by vesical afferents, and produces a rebound excitation eliciting the afterdischarge. 3. An inhibition of the rectal outflow occurred simultaneously with waxing of the vesical outflow during constant afferent stimulation of the vesical and rectal branches of the pelvic nerve in dogs from which the colon and urinary bladder had been removed. This inhibition may be produced by an efference copy from the pontine micturition reflex center. Most recto-colonic branches of the nerve responded to vesical distention with these inhibitions and afterdischarge. Corresponding to these responses colonic motility was inhibited and/or enhanced. 4. Eleven of 26 recto-anal branches of the nerve responded to vesical distention with an enhanced outflow elicited simultaneously with an enhanced vesical outflow. This enhancement was abolished by transection of C1, which indicates that it may be caused by an efference copy from the pontine micturition reflex center.