Non-adrenergic non-cholinergic nerve-mediated inhibitory control of pigeon oesophageal muscle.
Pigeon oesophageal smooth muscle in vitro has spontaneous electromechanical activity. In the presence of atropine and guanethidine, electrical field stimulation evokes a transient TTX-sensitive response comprising inhibition of electric bursting activity and muscular relaxation. This NANC inhibitory response was analysed using the K+ channel blockers TEA and apamin, TEA perfusion (0.1-5 mM) induced a concentration-dependent reduction in amplitude of EFS-evoked relaxation. Responses to higher stimulation frequencies were more sensitive to TEA than those to lower ones. The maximum reduction in amplitude (29% of control) was obtained on 30 Hz EFS evoked responses during 5 mM TEA perfusion. In a similar way, apamin (0.01-10 microM) perfusion reduced NANC relaxation, up to 30% of control. These results suggest that in the pigeon oesophagus, NANC intramural neurons are responsible for muscular relaxation. We speculate that an increase in K+ conductance might be the main mechanism involved, although the residual response after K+ channel blockade indicates the existence of an additional ionic mechanism.
Bonvissuto
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Dipartimento di Biologia Cellulare e dello Sviluppo, Università degli Studi di Palermo, Italia.
Vetri
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Fileccia
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Postorino
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Abbadessa Urso
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D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D010856:Columbidae; D004305:Dose-Response Relationship, Drug; D004947:Esophagus / Q000294:innervation*; D005071:Evoked Potentials; D006145:Guanethidine / Q000494:pharmacology; D009130:Muscle, Smooth / Q000294:innervation*; D009433:Neural Inhibition; D015221:Potassium Channels / Q000187:drug effects; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D001030:Apamin; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D001285:Atropine; D006145:Guanethidine