Peristalsis and antiperistalsis in the chicken caecum are myogenic

Peristalsis in the chicken caecum was investigated by recording the responses of isolated segments of the caecum to either fluid distension using a modified Trendelenburg apparatus or by monitoring circular muscle activity following localized radial distension of adjacent areas. Raising the intraluminal pressure did not initiate peristalsis except in the presence of tetrodotoxin, local anaesthetics and high concentrations of phentolamine. The effect of these drugs was reversible. Localized distension generally produced either a small relaxation of the circular muscle or no response at all on both sides of the site of distension. After exposure to tetrodotoxin one, or more (usually several), rhythmic propogating contractions were initiated at the point of distension. These results suggest that intrinsic inhibitory neurones are present in the caecum and may be triggered by distention. The possible role of these inhibitory neurones in the emptying and filling of the caecae is considered.