Neurochemical evidence for the activation of the 'efferent' function of capsaicin-sensitive nerves by lowering of the pH in the guinea-pig urinary bladder.
Lowering of the pH of the superfusion solution (physiological phosphate buffers derived from normal Krebs solution) of mucosa-free muscle strips of the guinea-pig urinary bladder from 7.4 to 6 or 5, produced a marked increase of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) outflow (total evoked release being 1677 +/- 287 fmol/g/35 min and 5283 +/- 484 fmol/g/35 min, respectively). The increase in CGRP-LI outflow evoked by exposure to pH 5 was abolished in strips pre-exposed to capsaicin (10 microM for 20 min), and was reduced by approximately 80% when superfusion was performed with Ca2(+)-free media. After application of pH 5 solution, capsaicin (10 microM) evoked a CGRP-LI release that amounted to 21% of controls. It is concluded that lowering of the pH induces a Ca2(+)-dependent release of CGRP-LI from capsaicin-sensitive nerves in the guinea-pig urinary bladder.
Geppetti
P
P
Institute of Internal Medicine IV, Florence University, Italy.
Tramontana
M
M
Patacchini
R
R
Del Bianco
E
E
Santicioli
P
P
Maggi
C A
CA
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology*; D004525:Efferent Pathways / Q000502:physiology*; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D009092:Mucous Membrane / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects / Q000293:injuries* / Q000502:physiology
D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin; D002118:Calcium