MYENTERIC REFLEX

Abstract

Local stimulation of the intestine produces responses which spread considerably beyond the stimulated area. Under certain conditions the contraction is restricted to the oral side. Such polar responses, which are designated as the myenteric reflex, may consist merely of an increase in the strength of the rhythmic contractions or they may be more prolonged contractions, chiefly of the circular muscles. The most effective stimulus for the myenteric reflex is longitudinal stretching in the small intestine of the rabbit, stroking the mucosa in the small intestine of the dog. Abnormal stimuli such as -electric stimuli or pinching often produce ascending and descending contractions. However, electric stimulation always produces a strictly polar response in the proximal colon of the rabbit, and in other parts of the intestine if the stimuli are close to threshold. Nicotine in low concentrations applied locally prevents the spread of the response from the stimulated area. Local application of acetylcholine in minimal concns. produces a polar response like that caused by appropriate mechanical or electrical stimulation. It is concluded that a synaptic mechanism consisting of short neurons and conducting chiefly in an aboral direction is involved in the myenteric reflex. The results are in agreement with the conclusion that the spontaneous contractions of the intestine are myogenic but are ordinarily conducted for only a short distance. The myenteric reflex increases this activity on the oral side and thereby propels the contents of the intestine. The reflex response by itself is not propagated. The-peristaltic waves depend on the continuous stimulation by the contents of the intestine.