Electrical stimulation of glossopharyngeal nerve and oesophageal EMG response in the pigeon

Abstract

The effects of the efferent glossopharyngeal nerve stimulation, on EMG activity of the pigeon cervical oesophagus, were studied. In control animals, stimulation caused a biphasic response characterized by an intra-stimulus excitatory component followed by a post-stimulus inhibitory one. The EMG response to glossopharyngeal stimulation appeared simultaneously throughout the cervical oesophagus. A bell-shaped mechanical wave was detected relating to the electrical excitatory component. Atropine administration antagonized the excitatory component, while the inhibitory one persisted. It occurs intra-stimulus, and its duration is increased, compared to control ones. A reduction in the oesophageal resting pressure was observed relating to the electrical inhibitory component. Hexamethonium caused complete disappearance of any EMG response to glossopharyngeal stimulation, as well as suppression of mechanical responses. The comparison between the EMG responses to swallow and to efferent glossopharyngeal stimulation suggests that in pigeon cervical oesophagus: primary peristalsis is central in origin; a dual system of glossopharyngeal fibres, excitatory and inhibitory, carries the central control for oesophageal motility; these excitatory and inhibitory fibres supply the oesophageal muscle via intramural neurons; the synaptic arrangement of the inhibitory pathway is more complex than the excitatory one.

Involvement of purinergic nerves in the NANC inhibitory junction potentials in pigeon oesophageal smooth muscle

“…It is known that non‐adrenergic non‐cholinergic (NANC) inhibitory neurones innervate the gastrointestinal smooth muscle of different vertebrate species (Watson, Taylor & Bywater, 1994; Spencer, Bywater, Holman & Taylor, 1998). NANC nerves in the pigeon cervical oesophagus have been described (Postorino, Serio, Fileccia, Mulè & Abbadessa Urso, 1985), as well as their important role in the development of the correct motor pattern during primary peristalsis (Fileccia, Postorino, Serio, Mulè & Abbadessa Urso, 1984).…”