2.3. Drugs

The drugs used were BPA (Tokyo Chemical Industries, Co. Ltd., Tokyo, Japan), 17β-estradiol, 4-OHT (≥98% trans isomer), pramoxine hydrochloride (Sigma-Aldrich, St. Louis, MO, USA) and prilocaine hydrochloride (Wako Pure Chemical Industries, Ltd., Osaka, Japan). All of the drugs (except for pramoxine and prilocaine, which were directly dissolved in Ringer's solution) were first dissolved in dimethyl sulfoxide (DMSO) to make a stock solution, and then diluted to the desired concentrations in Ringer's solution immediately before use, where the concentration of DMSO was less than 1%. BPA, 17β-estradiol and 4-OHT were tested at concentrations less than their highest dissolvable concentration.