Evidence against vasoactive intestinal polypeptide (VIP) as a dilator and in favour of substance P as a constrictor in airway neurogenic responses.
Propranolol-resistant neurogenic relaxation persisted in (carbachol-contracted) guinea-pig tracheae already relaxed by supramaximal concentrations of vasoactive intestinal polypeptide (VIP). Also, VIP relaxed preparations that were under neurogenic inhibition. In hilus bronchi, about 60% of a neurogenic contraction was atropine-resistant. (Arg5, D-Trp7.9) SP 5-11 specifically antagonized this contraction and those produced by exogenous substance P. Substance P, but not VIP, seems to be involved in nerve-mediated effects on guinea-pig airway tone.
D000818:Animals; D001980:Bronchi; D004558:Electric Stimulation; D006168:Guinea Pigs; D009119:Muscle Contraction; D009126:Muscle Relaxation / Q000187:drug effects; D009469:Neuromuscular Junction / Q000502:physiology; D013373:Substance P / Q000502:physiology*; D014132:Trachea; D014660:Vasoactive Intestinal Peptide / Q000502:physiology*
D013373:Substance P; D014660:Vasoactive Intestinal Peptide