[Responses of narrow segments of intestines in the congenital aganglionosis rat to various stimulants].

The shortenings of intestinal strips isolated from narrow segments in the aganglionosis rat have been studied in response to stimulants and field stimulation. Relating to the action of nicotine, eserine and field stimulation, the number of exogenous nerve bundles observed between the longitudinal and circular muscle layer and the type of cells existing in the nerve bundles were examined by light and electron microscopes. Nicotine shortened in 16 out of 31 narrow segments and eserine 13 out of 14 preparations. In 6 out of 21 preparations, field stimulation produced weak contraction, which was abolished by pretreatment of atropine or TTX. The number of the nerve bundles was larger in the responded groups than in the non-responded. However, no ganglion cells were observed in the nerve bundle of the narrow segment of the aganglionosis rat. To acetylcholine, serotosine, prostaglandin E2, KCl and BaCl2, all narrow segments responded, though the response to these drugs particulary to KCl was extremely weaker than those in control. It is suggested that the nerve bundles of the narrow segment branched and formed nerve endings in the smooth muscle and the responsiveness of the receptor to the stimulants is maintained in the narrow segment, but contractility of the smooth muscle is small.