Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The stimulatory effect of dopamine (DA) on the release of oxytocin (OT) in lactating rats is exerted at the D-1 DA receptor subtype. Because the neural loci mediating this effect have not been identified, the objective of the present studies was to test whether OT release in the lactating rat would be elevated after central administration of a D-1 DA receptor agonist into the third ventricle (3V) or directly into either the rostral paraventricular/anterior commissural nucleus area (PVN/ACN), the central paraventricular nucleus area, or the supraoptic nucleus (SON), all of which contain OT neurosecretory cells. Lactating rats were implanted with a stainless steel cannula directed into one of the above areas or into the arcuate-ventromedial region of the medial basal hypothalamus (MBH), or sites dorsal to the PVN/ACN or SON, which served as anatomical controls. After 6-7 days of recovery, each animal received an intra-atrial cannula for sequential blood sampling, and was used in experiments 24 h later. Animals were separated from their litters, and following a period of basal blood sampling, received central microinjections of either vehicle, the D-1 DA receptor agonist SKF-38393, or the D-2 DA receptor agonist quinpirole, and blood samples were removed periodically for 60 min. An injection of angiotensin II (Ang II, 100 ng) was made into each site as a positive control for OT release.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Activation of central D-1 dopamine receptors stimulates oxytocin release in the lactating rat: evidence for involvement of the hypothalamic paraventricular and supraoptic nuclei. 143 76

A cell-by-cell analysis of the magnocellular elements in hypothalami of fifty Long-Evans (normal) and Brattleboro (diabetes insipidus) rats was done using the unlabeled antibody enzyme technique (PAP) with primary antisera directed against oxytocin (OXY), vasopressin (ADH), and the neurophysins. The magnocellular neurons of the hypothalamus were found in the supraoptic (SON), paraventricular (PVN), and anterior commissural (ACN) nuclei, a number of accessory nuclei, and as individual cells in the anterior hypothalamic area. SON was divided by the optic tract into the principal part and retrochiasmatic SON. In retrochiasmatic SON a majority of the cells contained vasopressin. Within the principal part of SON oxytocin-producing cells tended to be found rostrally and dorsally, while the vasopressin cells were more common caudally and ventrally. PVN was divided into three subnuclei, the medial, lateral, and posterior subnuclei, on the basis of cellular morphology and peptide content. The magnocellular cells of the medial and lateral PVN were closely packed together and nearly round, while those of posterior PVN were more separated and fusiform in shape with their long axis running in a medio-lateral direction. Medial PVN consisted primarily of oxytocin-producing cells, while lateral PVN was formed by a core of vasopressin-producing cells with a rim of oxytocin cells. Posterior PVN contained largely oxytocin-producing cells. Both ADH and OXY cells were found in the accessory nuclei. In the Long-Evans rat the SON had, on the average, 1443 OXY and 3236 ADH cells; the PVN had 1174 OXY and 976 ADH cells; and the accessory magnocellular groups in the hypothalamus (including the ACN) had 1286 OXY and 552 ADH cells. The Brattleboro strain animal had similar numbers of cells in these nuclei. (The cells which contain ADH in normal animals were identified in the Brattleboro rat as large, neurophysin-negative cells.) Thus, a large fraction of the magnocellular oxytocin- and vasopressin-producing cells in the rat were located outside of the PVN and SON. One accessory cell group in particular, ACN, had 616 OXY cells, or about 50% as many as PVN. In each nucleus the sum of the numbers of OXY and ADH cells was approximately the number of neurophysin cells.
 ...
PMID:Immunohistochemical analysis of magnocellular elements in rat hypothalamus: distribution and numbers of cells containing neurophysin, oxytocin, and vasopressin. 701 60

The possible cooperation of neuropeptide Y (NPY) and alpha-1-adrenergic mechanisms in the release of oxytocin (OT) in conscious, nonsuckled lactating rats was examined following microinjections of NPY and its analogs and/or alpha-adrenergic drugs into the supraoptic nucleus (SON) or anterior paraventricular nucleus/anterior commissural nucleus (PVN/ACN). The alpha-1-adrenergic agonist phenylephrine dose dependently increased plasma OT after injection into the SON or the PVN/ACN, and this was prevented by treatment with the specific alpha-alpha-1-adrenergic receptor antagonist prazosin, but not by the alpha-2 antagonist rauwolscine. The alpha-2-adrenergic agonist clonidine did not increase plasma OT. Injection of NPY or of the related peptide YY (PYY) alone into the SON or the PVN/ACN also dose dependently increased plasma OT; this was also significantly attenuated by prazosin. Plasma OT responses to NPY and PYY differed significantly in dynamics and duration, which may be related to large differences found in the patterns of displaceable binding of [125I]NPY and [125I]PYY to hypothalamic membranes. The stimulatory action of NPY was mimicked by a preferential Y-1 receptor agonist, but not by an agonist of the Y-2 NPY receptor. Coinjection of NPY or PYY and phenylephrine into either the SON or the PVN/ACN area produced a greater than additive discharge of OT, especially in the SON. This increase was mostly due to a markedly enhanced initial release of OT, and was also completely eliminated by prazosin. The NPY-alpha-1 interaction in stimulating plasma OT was not mediated by direct binding of the peptides to alpha-1-adrenergic receptor sites. These results indicate that 1) the stimulatory noradrenergic influence on OT secretion in the lactating rat is mediated by the alpha-1 adrenergic receptor via an action in the PVN/ACN and SON; 2) NPY also stimulates OT secretion in the lactating rat through the Y-1 receptor subtype in the PVN/ACN and SON; 3) NPY markedly enhances the OT secretory responses to alpha-1 receptor stimulation, particularly in the SON. The cooperative stimulation by NE and NPY may be of physiological importance in mediating the episodic release of OT in response to suckling.
 ...
PMID:Central stimulation of oxytocin release in the lactating rat: interaction of neuropeptide Y with alpha-1-adrenergic mechanisms. 838 Oct 69

Previous studies have implicated oxytocin (OT) in the control of surge-type PRL secretion in the pregnant and pseudopregnant rat. The present studies examined the relationship between mating-induced activation of OT neurons in the paraventricular (PVN), supraoptic (SON), and anterior commissural (ACN) nuclei and PRL secretion. Activity within OTergic neurons, as measured by increased c-fos expression, was examined immediately and 5 days following mating in ovariectomized, estrogen-plus-progesterone-treated rats at the time when nocturnal PRL surges are expressed (0600 h) and at an intersurge time (2400 h). Females received fifteen intromissions (15I), 15 mounts-without-intromission (MO), or no stimulation (homecage, HC) from a sexually experienced male. Receipt of 15I at 0600 h induced significantly higher numbers of OT immunoreactive (OT-IR) cells and FOS/OT-IR double-labeled cells in the parvocellular division of the PVN (PVNparv) and in the SON than did 15I at 2400 h. Numbers of OT-IR and FOS/OT-IR cells in the ACN and in the magnocellular compartment of the PVN (PVNmag) were not influenced by mating at either time. In contrast, acute PRL secretion induced within 5-30 min by 15I was not influenced by whether mating occurred at 1800 h (diurnal surge), 2400 h, or 0600 h, nor were plasma OT levels elevated during the 1 h following 15I or MO at these times. Examination of FOS-IR cells throughout the hypothalamus across the two times of day revealed previously unreported differences between 15I and control MO treatments in the PVN, SON, and the ventrolateral part of the arcuate nucleus (ARCvl). On day 5 post mating, numbers of OT-IR and FOS/OT-IR cells in the PVN, SON, and ACN were very low and were similar between 0600 h and 2400 h and between females that showed (15I) or did not show (MO) mating-induced PRL surges characteristic of pregnancy. The results of these studies demonstrate that intromissive but not mounts-only stimulation from males induces a rapid increase in OT-IR staining and OT neuron activation in the PVNparv and the SON. These mating-induced responses in OT neurons occurred within 1 h after mating only at 0600 h, suggesting a diurnal fluctuation in sensitivity to intromissive stimulation. Changes in OTergic function were not seen in response to mating at other times of day, nor at the time of the nocturnal PRL surge 5 days after mating. We conclude that OT activity induced by mating does not act to stimulate PRL secretion directly, but may be involved in the process(es) by which genitosensory stimulation initiates surge-type PRL secretion.
 ...
PMID:Diurnal fluctuations in mating-induced oxytocinergic activity within the paraventricular and supraoptic nuclei do not influence prolactin secretion. 983 21