Acetylcholine

Human motilin was purchased from Anygen Co., Ltd (GwangJu, Korea). Erythromycin was purchased from Mylan (Tokyo, Japan). Acetylcholine (ACh), atropine and tetrodotoxin (TTX) were purchased from Wako Pure Chemical (Osaka, Japan). For in vivo experiments (gastric emptying), erythromycin was diluted in physiological salt solution. The dose of erythromycin was expressed as mg/kg body weight. For in vitro experiments (contraction), erythromycin was diluted in, and other drugs were dissolved in, physiological salt solution. Drug concentrations were expressed as final molar concentrations in the organ bath solution. All drugs were prepared immediately before use.

OT and OTRA [d(CH₂)₅Tyr(Me)²,Thr⁴,Tyr-NH₂⁹]-vasotocin were purchased from Bachem (Bachem Peninsula Laboratories, Inc., Bubendorf, Switzerland). U73122 was obtained from Sigma (St. Louis, MO, USA). Isoproterenol, pertussis toxin, acetylcholine, forskolin, and other chemicals were from Wako Pure Chemical Industries (Osaka, Japan). OT and OTRA were dissolved in 5% acetic acid, while U73122 and forskolin were dissolved in dimethyl sulfoxide (DMSO) as stock solutions (5–20 mM), and then diluted to final concentrations in cell culture solutions. The final concentration of DMSO or acetic acid in the bathing solution was 0.01% or less. Prior to electrophysiological and real-time PCR analyses, these concentrations of DMSO or acetic acid were confirmed not to significantly influence I_Ca.L or Cav1.2 mRNA expression.