Murine intestinal migrating motor complexes: longitudinal components

Spontaneous migrating contractions have been described in the circular muscle of the isolated mouse colon and terminal ileum, however, spontaneous events equivalent to these have not been reported in the longitudinal muscle. The longitudinal muscle shortenings in the colon and ileum, which are of similar form, frequency and pharmacology to the circular muscle colonic and ileal migrating motor complexes (CMMCs and IMMCs), are recorded in the present study. The spontaneous ileal and colonic longitudinal muscle shortenings appear to be neurally organized as they are abolished by tetrodotoxin (1 mu mol L-1 ), hexamethonium (500 mu mol L-1 ) and morphine (1 mu mol L-1 ). Endogenously released nitric oxide slowed the frequency of spontaneous ileal and colonic longitudinal muscle shortenings and 5-hydroxytryptamine increased their frequency. Hyoscine (1 mumol L-1 ) abolished longitudinal shortenings in the ileum and reduced the amplitude of longitudinal shortening by similar to44% in the colon. Shortenings were effectively abolished by nifedipine (1 mumol L-1 ). Surgical sectioning of the colon identified that each region of the colon contracted longitudinally in an independent fashion; the distal colon contracted to the greatest amplitude and lowest frequency. The longitudinal preparation is suitable to initially assess the actions of novel pharmacological agents on spontaneous, neurally coordinated, CMMCs and IMMCs in emptied isolated murine intestines.