Noradrenaline affects secretory function of corpus luteum independently on prostaglandins in conscious cattle

The aim of this study was to examine whether prostaglandins are involved in the effects of noradrenaline on corpus luteum (CL) function. To establish an effective dose of indomethacin (INDO) to prevent prostaglandin synthesis, different doses (120, 180, 240 and 300 mg) of drug were infused for 30 min on days 17-18 of the estrous cycle in four heifers and followed with 50 IU of OT. Plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were measured, both to illustrate the concentrations of all prostaglandins and to establish the effective dose of INDO that can effectively block prostaglandins synthesis. In Experiment 2, on days 10-12 of the cycle, heifers (n = 6) were infused in a Latin square design with 4 mg of noradrenaline (NA) and pre-treated with 120 mg of INDO or with saline. In both cases, NA did stimulate progesterone and ovarian oxytocin secretion. We conclude that NA affects secretory function of the CL independently of prostaglandins.