Antagonism of non-cholinergic excitatory junction potentials in the guinea-pig ileum by a substance P analogue antagonist.
In the presence of atropine electrical transmural stimulation (using repetitive volleys, e.g. 3 pulses at 50 Hz applied every 4 s) of full thickness longitudinal strips of guinea-pig ileum produced non-cholinergic excitatory junction potentials (EJPs) and inhibitory junction potentials (IJPs) in the circular muscle layer. After abolition of the IJPs with apamin, the non-cholinergic EJPs clearly showed facilitation. In the presence of apamin and the substance P analogue antagonist, [D-Arg1,D-Pro2,D-Trp7-9,Leu11]-substance P (SPA), the non-cholinergic EJPs were reduced by 60-90%; transmural stimulation now revealed an apamin-resistant IJP followed by a slow depolarization. The atropine-resistant EJPs are probably caused by the release of substance P (or a similar compound) and are likely to underlie the non-cholinergic contractions reported to occur in this tissue.
Taylor
G S
GS
Bywater
R A
RA
D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects*; D006168:Guinea Pigs; D007082:Ileum; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009433:Neural Inhibition / Q000187:drug effects*; D013373:Substance P / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D013373:Substance P; C038073:substance P, Arg(1)-Pro(2)-Trp(7),(9)-LeuNH(2)(11)-