2.5 Drugs
H2O2, HC-03003, AITC, capsaicin, tetrodotoxin (TTX) and Carbachol were purchased from Sigma-Aldrich (Darmstadt, USA). While PGE2, SP and a selective antagonist of neurokin-2 receptors (NK2Rs), SR 48968, were sourced from MCE (New Jersey, USA).
Stock solution of capsaicin were prepared in 100% ethanol and stored at −20 ℃ until use. AITC, SR 48968, PGE2, and SP solutions were made in dimethyl sulfoxide and diluted immediately before use. TTX was dissolved in deionized water. The final concentrations of ethanol or dimethyl sulfoxide were <0.1%. In all experimental groups, at least one parallel control experiment was carried out in vehicle. The vehicles we used had no pharmacological effects on the tone of preparations or agonist-induced contractions. Chemicals were used at concentrations shown to be effective in preliminary experiments, or at concentrations used in studies published previously[29, 30].