Enteric co-innervation of striated muscle in the esophagus: still enigmatic?

Abstract

The existence of a distinct ganglionated myenteric plexus between the two layers of the striated tunica muscularis of the mammalian esophagus has represented an enigma for quite a while. Although an enteric co-innervation of vagally innervated motor endplates in the esophagus has been suggested repeatedly, it was not possible until recently to demonstrate this dual innervation. Twenty-two years ago, we were able to demonstrate that motor endplates in the rat esophagus receive dual innervation from both vagal nerve fibers originating in the brain stem and from varicose enteric nerve fibers originating in the myenteric plexus. Meanwhile, a considerable amount of data has been gathered on enteric co-innervation and its occurrence in the esophagus of a variety of species including humans, its neurochemistry, spatial relationships on motor endplates, ontogeny and possible functional roles. These data underline the significance of this newly discovered innervation component, although its function in vivo is still largely unknown. The aim of this review, which is an update of our previous paper (Wörl and Neuhuber in Histochem Cell Biol 123(2):117-130. doi: 10.1007/s00418-005-0764-7 , 2005a), is to summarize the current knowledge about enteric co-innervation of esophageal striated muscle and to provide some hints as to its functional significance.

ATP-dependent potassium channels contribute to motor regulation of esophageal striated muscle in rats

“…The external muscle layer of the mammalian esophagus contains not only smooth muscle fibers but also striated muscle fibers, in contrast to other gastrointestinal tracts such as the stomach, small intestine and large intestine [23, 37]. The distributions of striated and smooth muscles are known to vary extremely among animal species [1, 29].…”

Characterization of peristaltic motility in the striated muscle portion of the esophagus using a novel in vivo method in rats

“…Striated muscle portion of the esophagus has morphological features: intrinsic nerves innervate motor endplates on striated muscle cells, an innervation pattern known as “enteric co‐innervation,” which compose a functional local neural circuit . As the neural circuit involving intrinsic nitrergic neurons in the esophagus wall inhibits acetylcholine release from the vagus nerve, we expected that administration of L‐NAME, a typical inhibitor of NOS to block NO production, would enhance the peristaltic response.…”

Neuronal Control of Esophageal Peristalsis and Its Role in Esophageal Disease

“…Apart from this extrinsic cholinergic innervation, the esophageal striated muscle portion contains a myenteric plexus with cholinergic and nitrergic neurons. These enteric neurons also innervate esophageal striated muscle that might be responsible for inhibitory modulation of striated muscle [4][5][6]. However, the central nervous system (CNS) plays the main role in controlling the initiation of peristalsis in the proximal esophagus.…”