Desensitization and capsaicin-induced release of substance P-like immunoreactivity from guinea-pig ureter in vitro.
Substance P-like immunoreactivity was assayed in superfusates of guinea-pig ureters following stimulation of afferent fibres with capsaicin, potassium chloride and the calcium channel agonist Bay K 8644. Capsaicin-evoked release of substance P-like immunoreactivity was calcium-dependent but unaffected by cobalt. Under appropriate conditions release was dose-related (ED50 = 610 nM) and reproducible. Selective desensitization to capsaicin could be demonstrated following prolonged exposure to different doses of capsaicin. No desensitization to capsaicin was observed following afferent fibre stimulation with a combination of Bay K 8644 and K+, which released a similar amount of substance P-like immunoreactivity as a desensitizing capsaicin stimulus. These data suggest that depletion of releasable substance P-like reactivity is unlikely to account for selective desensitization of ureteric primary afferent fibres to capsaicin.
Dray
A
A
Sandoz Institute for Medical Research, London, U.K.
Hankins
M W
MW
Yeats
J C
JC
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D051379:Mice; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*; D014513:Ureter / Q000294:innervation*
D013373:Substance P; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002211:Capsaicin; D002118:Calcium