LOCAL NERVE NETWORKS-MEDIATED ACTIVITY OF COLO-RECTAL LONGITUDINAL AND CIRCULAR MUSCLES IN RAT MODEL

Mechanographic on-line technique and electrical fie:id stimulation (0.8 ms, 40 V, 2 Hz, 20 s) were used to evaluate the motor responses of longitudinal and circular muscles isolated from rat colon and rectum as model preparations to display excitation of local enteric nerve networks in the large intestine. The local responses of longitudinal muscle strips isolated from proximal and distal parts of the colon and rectum were contractions. There were no differences between the peak amplitude in the motor responses of the longitudinal muscles which belonged to the colon or to the rectum. The modular contractile responses of the circular muscle rings from both parts of the colon and the middle part of the rectum were significantly less pronounced than the local responses of the longitudinal muscle strips. The electric ally-induced responses of the colonic and rectal muscles were tetrodotoxin (0.1 mu M)-sensitive. The results show that low frequency-sensitive excitatory neurotransmission more expressed to the longitudinal muscle dominates in the local nerve networks of the rat colon and rectum suggesting an essential role of cob-rectal contractile mechanisms in propelling the gut content in anal direction.