The Effect of Distension of Distal Colon and Rectum on Micturition Reflex in Rats

Kim, Hyoung Jin; Lee, Jeong Gu

Abstract

PURPOSE: Bowel distention stimulates neuroreceptors inside bowel wall with resultant effect to the bladder activity via segmental spinal reflex. This work aimed to elucidate the effects of distal colon and rectum distension on the micturition reflex.
MATERIALS AND METHODS
The experiments were performed on female Sprague Dawley rats anesthetized with intraperitoneal urethane (1.25g/kg), weighing 250-350g. Intravesical pressure was measured by a conventional pressure transducer. Isovolumetric bladder contractions were recorded during distension of the distal colon and rectum. The frequency of voiding contractions was calculated by counting the number of peaks/10mins. of observation and the mean amplitude of the contractions were recorded from the cystometrogram. During maximal distention of the bowel, changes of the micturition reflex were observed repeatedly after injection of acetylcholine, phenylephrine and adenosine triphosphate (ATP).
RESULTS
The frequency and amplitude of micturition reflex decreased significantly compared to baseline during incremental distension of the rectum. whereas, frequency was increased and amplitude was decreased significantly during distension of the distal colon. The micturition reflex inhibited by distension of the rectum was restored by acetylcholine.
CONCLUSIONS
The micturition reflex was inhibited by distension of the rectum and restored by acetylcholine. This result indicated that the inhibition of the micturition reflex caused by distension of the rectum is related to parasympathetic nerve activity. With this results, it may be suggested that the constipation or abdominal distension due to intestinal motility disorder are associated with voiding dysfunction clinically.