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.