Christensen J, Lund G F
J Clin Invest. 1969 Feb;48(2):408-19. doi: 10.1172/JCI105998.
The opossum esophagus contains only smooth muscle in the distal two-thirds; it can be used to study autonomic control of esophageal smooth muscle. Three different preparations of opossum esophagus were used; the esophagus in vivo, the isolated whole esophagus, and isolated strips of the three layers of esophageal smooth muscle. Responses were examined to localized distension and to electrical stimulation. Distension of the esophagus in vivo produced three separate responses: inflation of a distending balloon caused a brief contraction rostral to the point of distension, the on response; maintenance of distension produced shortening of the esophagus, sustained for the duration of the distension, the duration response; and deflation of the balloon caused a single brief caudal circumferential contraction, apparently propagated caudad, the off response. In the isolated whole esophagus distension produced the same three responses. Electrical stimulation in this preparation produced apparently identical responses. Electrical stimulation of isolated strips of the three muscle layers showed that the muscularis mucosae and the longitudinal layer of the muscularis propria always respond with a duration response only. The circular layer of the muscularis propria responds with on and off responses only. These observations suggest that both types of stimuli excite the same afferent nerve fibers in local reflex pathways. Peristalsis can be maintained by these reflexes in the smooth muscle part of the esophagus independent of central nervous connections.
负鼠食管的远端三分之二仅含平滑肌；它可用于研究食管平滑肌的自主控制。使用了三种不同的负鼠食管标本：体内食管、离体全食管以及食管平滑肌三层的离体肌条。检测了对局部扩张和电刺激的反应。体内食管扩张产生三种不同的反应：扩张球囊充气会在扩张点上方引起短暂收缩，即开启反应；持续扩张会使食管缩短，并在扩张期间持续，即持续反应；球囊放气会引起单次短暂的尾侧环周收缩，显然是向尾侧传播，即关闭反应。在离体全食管中，扩张产生相同的三种反应。在此标本中进行电刺激产生的反应明显相同。对三层肌层的离体肌条进行电刺激显示，黏膜肌层和固有肌层的纵行层总是仅产生持续反应。固有肌层的环形层仅产生开启和关闭反应。这些观察结果表明，两种类型的刺激在局部反射通路中激发相同的传入神经纤维。这些反射可在食管平滑肌部分维持蠕动，而与中枢神经连接无关。
