IMMUNOCYTOCHEMICAL LOCALIZATION OF VASOACTIVE-INTESTINAL-PEPTIDE AND NEUROPEPTIDE-Y IN THE BOVINE OVARY

The distribution of the neuropeptides vasoactive intestinal peptide (V IP) and neuropeptide Y (NPY) was studied immunocytochemically in bovin e ovaries from 3 mo of gestation up to and including puberty, and from adult cows at three stages of the estrous cycle. The appearance of VI P and NPY immunoreactivity of 4.5-6 mo of gestation coincided with the onset of follicular development. In contrast to NPY, VIP was first fo und in the cortex. Both VIP and NPY immunoreactivity increased with ag e. From 9 mo of gestation onwards, VIP and NPY were found around blood vessels and non-vascular smooth muscle cells, in the stroma near prea ntral follicles, and in the theca externa of antral follicles. In addi tion, VIP-positive cells were observed exclusively in the granulosa la yer of the preovulatory follicle at the time of the LH surge. The dist ribution of VIP- and NPY-immunoreactive fibers in the ovary may point to an effect of these neuropeptides on various physiological processes , including follicle development and ovarian blood now. In addition, t he presence of VIP-positive cells in the granulosa layer of the preovu latory follicle is indicative of a role for VIP in ovulation.