الفهرس 
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Abstract
Colonic smooth muscle is controlled by its intrinsic xnyoelectrical activity which is composed of slow waves and spike potentials (Bortoff, 1969 and 1976). Further control of colonic motility is mediated through neural ref léxes or the effects of neurohumoral peptides on the underlying myoelectrical activity (Snape, 1975).
Slow waves are cyclical slow changes in the membrane potential of the colonic smooth muscle. Colonic slow waves are generated in the cells within the inner most layers of circular smooth muscle bordering on the submucosa in the dog (Durdle et al., 1983). The slow wave pattern is not constant throughout the colon. There is a frequency of 9 to 10 cycles/minute (c/m) from the ascending colon to the upper siginoid colon. The frequency decreases from the lower igmoid to the rectum where it appears to be 6 c/m (Taylor et al., 1975 and Sarna et al., 1980). In normal subjects, visual analysis of myoelectrical recording made from the rectosigmoid allowed the identification of two distinct
slow wave rhythms, a faster predominant rhythm with a frequency of 7 - 12 c/rn (high frequency wave rhythm i.e HFR) and a lower frequency rhythm, less frequently observed, with a frequency of 3 — 5 c/rn (Low frequency wave rhythm i.e LFR) (Couturier et al., 1969; Tayloret al., 1974; Daniel, 1975; Taylor et al., 1975 and Snape et al., 1976).
Slow waves are not related directly to oolonic contractions; however, they control the occurrence of spike bursts and hence of contractions in time and space (Sarna et al., 1980).
Spike potentials are rapid changes in membrane potential that occur at the peak of slow wave depolarization (Bortoff, 1969). The major type of spike activity is superimposed on slow wave activity and its frequency is controlled by the slow wave frequency (Snape et al., 1977). This type of spike activity causes a segmental type of contractile response, which most likely has a mixing function within the lumen of the colon (Sarna et al., 1981). Spike potentials can also exist as migrating spike bursts associated with a powerful contraction (Sarna et al., 1981).