Primary peristalsis in pigeon cervical oesophagus: two EMG patterns.

Swallowing elicits two propagated EMG peristaltic patterns in pigeon cervical oesophagus: i) "simple" peristaltic pattern and ii) "complex" peristaltic pattern. "Simple" peristaltic pattern is characterized by an intense, long-lasting burst of spikes, high in amplitude with an aboral increasing delay in onset. "Complex" peristaltic pattern presents an early short period of reduction in spontaneous electrical activity, followed by an excitatory period similar to that of "simple" pattern. The early inhibitory component has a very short delay in onset increasing aborally. Atropine abolishes the EMG excitatory component of both patterns, while the inhibitory period persists, showing increased duration and reduced propagation speed. "Simple" peristaltic pattern, mediated by cholinergic nerves, acting on muscular muscarinic receptors, is identifiable with an "on response". "Complex" peristaltic pattern shows a cholinergic muscarinic excitatory component and an atropine-resistant inhibitory component. This latter component is not a passive post-inhibitory rebound ("off response").