Surgical procedures
Pregnant rabbits were anaesthetised with ketamine and xylazine followed by intravenous injections of 15 mg/kg pentobarbital, and anaesthesia was maintained by additional doses as necessary for the first 30 min of the experiment23. A local anaesthesia of 1% lidocaine was injected subcutaneously into the left inguinal area and mid-lower abdomen. The adequacy of general anaesthesia was monitored by the loss of the ear pinch reflex. Rabbits were kept supine and spontaneously breathing on the warming plate to maintain the body temperature at 36-37°C. A 20-gauge catheter (polyethylene indwelling needle; Terumo, Tokyo, Japan) was aseptically introduced into the left femoral artery for measuring haemodynamics and blood sampling. The same size of the catheter was similarly inserted into the left femoral vein for fluid injections. After instrumentation, rabbits were stabilised for 10 min to record the baseline data.