title: Actions of noradrenaline on myenteric neurons in the guinea pig gastric antrum.
abstract: We used intracellular electrophysiological recording to study the actions of noradrenaline on myenteric neurons in the guinea pig gastric antrum. Noradrenaline caused a dose-dependent inhibition of the stimulus-evoked cholinergic fast excitatory postsynaptic potentials (EPSPs). Noradrenaline had no effect on the postsynaptic response to acetylcholine, suggesting a presynaptic site of action. The slow EPSP was also presynaptically inhibited by noradrenaline. In only 5% of the neurons, noradrenaline caused a postsynaptic depolarization, accompanied by increased input resistance and enhanced excitability. Studies with adrenergic antagonists and agonists revealed that the presynaptic inhibitory effect was mediated by an alpha 2-receptor, while the postsynaptic excitatory effect seemed to be mediated by an alpha 1 receptor. We conclude that noradrenaline inhibits neurotransmitter release from cholinergic and non-cholinergic nerve terminals in the myenteric plexus of the antrum and that it excites a subpopulation of antral neurons. Both mechanisms may contribute to the neurally mediated inhibitory action of noradrenaline on gastric contractility.
authors.affiliation: Department of Physiology, College of Medicine, Ohio State University, Columbus.
authors.forename: J F
authors.initials: JF
authors.lastname: Tack
authors.forename: J D
authors.initials: JD
authors.lastname: Wood
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D005769:Gastrointestinal Motility / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D009197:Myenteric Plexus / Q000166:cytology* / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D011706:Pyloric Antrum / Q000294:innervation / Q000502:physiology*; D013569:Synapses / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D003000:Clonidine; D000109:Acetylcholine; D009638:Norepinephrine