Cholinergic neurons are involved in the effect of substance P on the circular muscle of the guinea pig small intestine.
The mode of action of the excitatory neuropeptide substance P was studied on the circular muscle of the guinea pig ileum in vitro. Atropine or tetrodotoxin strongly inhibited substance P-induced phasic contractions. The atropine-resistant part of the circular response was blocked by tetrodotoxin. A newly-developed method for quantitative evaluation revealed a rightward displacement of the substance P concentration-response curve, as well as a strong depression of the maximum effect, in the presence of atropine. These results indicate that cholinergic (and probably also non-cholinergic) excitatory neurons mediate phasic contractions due to substance P. The tonic component of the substance P-induced contraction was slightly reduced by atropine.
Barthó
L
L
Department of Pharmacology, University Medical School, Pecs, Hungary.
Pethö
G
G
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000294:innervation; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010275:Parasympathetic Nervous System / Q000166:cytology / Q000502:physiology*; D012844:Sincalide / Q000494:pharmacology; D013373:Substance P / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
D013373:Substance P; D013779:Tetrodotoxin; D001285:Atropine; D012844:Sincalide; D000109:Acetylcholine