Abstract
The rectum possesses electric activity in the form of pacesetter (PPs) and action potentials (APs). In recent studies we suggested that the waves are not initiated by the extrarectal autonomic innervation but might be triggered by a ‘rectosigmoid pacemaker’ and are transmitted in the rectal wall through the rectal musculature and not the enteric nerve plexus. To investigate whether the rectal waves are transmitted through the circular or longitudinal muscle layer, the rectum of 18 mongrel dogs was exposed under anesthesia through an abdominal incision. Three electrodes were applied to the rectal wall (longitudinal muscle layer) and another 3 electrodes to the circular muscle; the latter was exposed by splitting apart the fibers of the longitudinal muscle. Rectal electric activity and pressure were recorded from the 6 electrodes before and after performing individual myotomy of the rectal longitudinal (9 dogs), circular (9 dogs), and then the whole muscle layers (18 dogs). The myotomy was performed proximal to and between the electrodes. Pacesetter (PPs) and action potentials (APs) were recorded from the 3 electrodes on the longitudinal muscle but no waves were registered from those on the circular muscle. After longitudinal muscle myotomy was performed between electrodes 1 and 2, PPs and APs were recorded from electrode 1 but not 2 and 3 and when performed proximally to electrode 1, no waves were registered. The rectal pressure increased concomitantly with occurrence of APs. Circular muscle myotomy effected no change in the rectal electric activity recorded from the 3 electrodes applied to the longitudinal muscle. In total muscle myotomy, the electric waves were recorded from the electrodes proximal but not distal to the myotomy. We propose that the motile activity of the rectal longitudinal muscle is initiated by the electric activity which appears to be triggered by the rectosigmoid pacemaker, while that of the circular muscle fibers is believed to be initiated by the stretch reflex induced by rectal distension. This concept is evidenced not only by the current findings but also by the histologic structure of the rectal musculature being of the unitary type of smooth muscles.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.