Immunocytochemical Localization of Vasoactive Intestinal Peptide and Neuropeptide Y in the Bovine Ovary

Abstract

The distribution of the neuropeptides vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) was studied immunocytochemically in bovine 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 VIP and NPY immunoreactivity of 4.5-6 mo of gestation coincided with the onset of follicular development. In contrast to NPY, VIP was first found in the cortex. Both VIP and NPY immunoreactivity increased with age. From 9 mo of gestation onwards, VIP and NPY were found around blood vessels and non-vascular smooth muscle cells, in the stroma near preantral follicles, and in the theca externa of antral follicles. In addition, VIP-positive cells were observed exclusively in the granulosa layer of the preovulatory follicle at the time of the LH surge. The distribution 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 flow. In addition, the presence of VIP-positive cells in the granulosa layer of the preovulatory follicle is indicative of a role for VIP in ovulation.

Participation of vasoactive intestinal polypeptide in ovarian steroids production during the rat estrous cycle and in the development of estradiol valerate-induced polycystic ovary

“…Evidence exists to document the presence of VIP mRNA in the rat ovary (Gozes & Tsafriri 1986). Later studies with bovine ovaries suggest granulosa cells as also a probable site of biosynthesis of VIP (Hulshof et al 1994).…”

“…A possibility to consider is that at least a fraction of the VIP regulation of estradiol release involves changes in locally produced VIP (Gozes & Tsafriri 1986, Hulshof et al 1994. From a regulatory perspective, it is difficult to compare levels of VIP used (10-6 M; w3700 ng/ml) in the in vitro studies with ovarian tissue levels of VIP (w150 pg/ovary).…”

“…Since granulosa cell compartment is also the site for VIP biosynthesis (Hulshof et al 1994) and the ovarian cysts seen in EV-treated rats have reduced granulosa cell layers (Brawer et al 1986, the similar intraovarian level of VIP in EV-treated and estrus rats may be reflective of increased innervation of the polycystic ovaries of the EV-treated rats. However, before establishing a role for VIP in the initiation of ovarian pathologies, detailed studies at individual follicle levels are required.…”

Alpha adrenergic receptors are involved in the contractile activity of neuropeptide Y in the porcine isolated ovarian artery

“…Moreover, the phase dependent changes in blood pressure after administration of NPY into the vessels pre-treated with α 1 -, and α 2 -adrenergic receptors agonists and α 1 -, and α 2 -adrenergic receptors antagonists were observed. It has been shown, that NPY is co-localized with NE in nerve fibres supplying blood vessels of the reproductive tract and that it affects the contractile activity of these vessels, in part via its own receptors and in part by the synergistic action with NE (Hulshof et al, 1994;Majewski et al, 1995). The studies of (Dynarowicz et al, 1988) have revealed that ovarian steroids affect the reactivity of adrenergic and cholinergic receptors in the porcine ovarian and uterine arteries as well as they change the process of release, intake and elimination of NE.…”

“…The presence of numerous NPY-IR nerve fibres around blood vessels in the reproductive tract suggests that NPY participates in the regulation of blood flow through these organs (Hulshof et al, 1994;D'Albora et al, 2000). NPY is localised alone, or it is co-localised with norepinephrine (NE) in nerve fibres supplying blood vessels of the reproductive tract.…”