Figure 11 - Gradient of cholinergic excitatory and noncholinergic inhibitory nerves in the smooth muscle portion of the esophagus.

The cholinergic excitatory innervation (open circles) is most marked in the proximal part and decreases gradually in the distal part. On the other hand, the inhibitory innervation (close circles) increases distally along the esophagus. As a result, upon stimulation the latency of contraction increases gradually distally along the esophagus, resulting in peristaltic sequence of contraction that is entirely located locally in wall of esophagus. (Source: Crist J, Gidda JS, Goyal RK. Intramural mechanism of esophageal peristalsis: roles of cholinergic and noncholinergic nerves. Proc Natl Acad Sci USA 1984; 81(11):3595–3599 with permission)