ABSTRACT
Recent observations indicate that the rat ovary receives not only adrenergic but also peptidergic innervation. In ruminants, there are few data available on the extent of a possible direct regulation of the peptidergic innervation of the ovary including the corpus luteum (CL). The direct effects of neuropeptide Y (NPY), substance P (SP) and vasoactive intestinal polypeptide (VIP) on the release of progesterone and oxytocin from midluteal phase CL (days 8–12) were examined in vitro. A possible direct neural influence might provide a sensitive short-term control. Long-term as well as short-term effects were assessed using both a serumreduced luteal cell culture and a microdialysis system (MDS) of luteal tissue. In the long-term experiments, luteal cells were preincubated from the start of the culture for 48 h with NPY, SP and VIP (10 pmol/l–100 nmol/l). During the following 4 h the neuropeptides showed a dose-dependent stimulation of progesterone release, but there was no effect on oxytocin release. LH showed a synergistic effect with NPY, SP and VIP on progesterone release. In the short-term experiments, the neuropeptides were added 48 h after the start of the culture. All three peptides were most stimulatory to LH-supported progesterone release 30 min after addition, and the effect decreased greatly thereafter to the control level from 60 to 120 min. In contrast, LH alone induced the maximal progesterone stimulation at 120 min. In the MDS, a 30-min perfusion with NPY, SP or VIP (10 nmol/l, 100 nmol/l and 1 μmol/l) induced significant acute effects on progesterone and oxytocin release. At 10 and 100 nmol/l the neuropeptides slightly inhibited progesterone release, but stimulated oxytocin release. At 1 μmol/l, however, both progesterone and oxytocin release were stimulated.
We conclude that neuropeptides NPY, SP and VIP act directly on progesterone and oxytocin release from bovine CL in vitro. The results suggest that the hormonal function of bovine CL may be partly influenced by peptidergic as well as adrenergic innervation.
Journal of Endocrinology (1993) 138, 451–458
