Distribution of vasopressin and oxytocin in rat brain

Arginine-vasopressin and oxytocin in various portions of rat brain were determined by radioimmunoassays. The hormones were extracted from tissue samples into 0.1 N HCl and then purified partially with acetone-petroleum ether extraction. The non-equilibration method was used for the assays. In this method recovery rates of arginine-vasopressin and oxytocin were 73.0 +/- 4.4% and 75.0 +/- 3.8%, respectively. Sensitivities of the assays were 1 pg of arginine-vasopressin and 0.75 pg (0.3 microU) of oxytocin per assay tube. The higher concentrations of arginine-vasopressin and oxytocin were confirmed in the hypothalamo-neurohypophyseal system, where these hormones are synthesized, transported and stored. Relatively high concentrations of these hormones, especially oxytocin, were detected in spinal cord. Amygdala, hippocampus, limbic forebrain and pineal body contained a certain amount of arginine-vasopressin (2-20 pg/mg protein). Oxytocin (1-7 pg/mg protein) was also detected in amygdala, pons and medulla oblongata, pineal body and midbrain. The low concentrations of these hormones were also found in cerebral cortex and cerebellum.     

Chromosomal and comparative mapping of rat oxytocin, oxytocin receptor and vasopressin genes

Oxytocin and its receptor are potentially important for cardiovascular functions. In the present paper, we report their chromosome locations in the rat and their comparative mapping with the mouse and human. They are located in chromosome regions previously known to contain quantitative trait loci for blood pressure in various genetic crosses. Thus, they have become valid candidate genes for genetic hypertension.     

Multiple signalling modalities mediated by dendritic exocytosis of oxytocin and vasopressin

The mammalian hypothalamic magnocellular neurons of the supraoptic and paraventricular nuclei are among the best understood of all peptidergic neurons. Through their anatomical features, vasopressin- and oxytocin-containing neurons have revealed many important aspects of dendritic functions. Here, we review our understanding of the mechanisms of somato-dendritic peptide release, and the effects of autocrine, paracrine and hormone-like signalling on neuronal networks and behaviour.     

Novel,potent, selective and brain penetrant vasopressin 1b receptor antagonists

Herein we report the discovery of a novel oxindole-based series of vasopressin 1b (V1b) receptor antagonists. Introducing a substituted piperazine moiety and optimizing the southern and the northern aromatic rings resulted in potent, selective and brain penetrant V1b receptor antagonists. Compound 9c was found to be efficacious in a rat model of anti-depressant activity (3?mg/kg, ip). Interestingly, both moderate terminal half-life and moderate bioavailability could be achieved despite sub-optimal microsomal stability.     

Neurotoxin effects on oxytocin, vasopressin and somatostatin in discrete rat brain areas

Monosodium-L-Glutamate (MSG) produces lesions to monoaminergic and peptidergic neurons in several brain areas. The present study examined the effect of neonatal MSG treatment on oxytocin (OXY), arginine-vasopressin (AVP) and somatostatin (SRIF) concentrations in several discrete brain areas of adult rats. OXY increased in the suprachiasmatic and arcuate nuclei and median eminence (ME) and decreased in the paraventricular nucleus of MSG-treated rats. MSG treatment caused AVP to increase in the arcuate nucleus and ME and decrease in the supraoptic nucleus. SRIF decreased following neonatal MSG treatment in both the ME and neurointermediate pituitary lobe. The results demonstrate that the effects of neonatal MSG treatment on neuropeptide content are not just limited to the arcuate nucleus. Furthermore, taken together with previous results, the data suggest that these changes may be indicative of functional deficits in the neuronal activity of some of these peptidergic neurons which, in turn, may be responsible for the abnormal secretion of several pituitary hormones observed in MSG-treated animals.     

Effect of restraint stress on rat brain serotonin

Restraint-induced stress in rats was found to enhance steady state concentrations of whole brain and hypothalamic serotonin, at 1,2 and 4 h after immobilization. The increase was maximal at 1 h and tended to decline thereafter. The rate of accumulation of rat brain serotonin, in pargyline pretreated animals, was significantly enhanced after restraint stress. Bilateral adrenalectomy and metyrapone, an endogenous corticoid synthesis inhibitor, failed to affect restraint stress (1h)-induced increase in rat brain serotonin levels. Thus restraint stress-induced autoanalgesia and potentiation of the pharmacological actions of several centrally acting drugs, in rats, are serotonin-mediated responses. The results also indicate that restraint stress-induced effects on rat brain serotonin are not dependent on endogenous corticoid activity.     

Localization of alpha1B-adrenergic receptor in female rat brain regions involved in stress and neuroendocrine function.

Activation of alpha1-adrenergic receptors has been linked to the control of blood pressure, neuroendocrine secretion, reproductive behavior and mood. The present study describes the distribution of alpha1B-adrenergic receptor immunoreactivity in female rat brain regions involved in stress and neuroendocrine function. The pattern of immunolabeling seen resembles that obtained in previous in situ hybridization studies. Several hypothalamic areas that control pituitary function showed intense fiber and/or cell immunolabeling, including the paraventricular nucleus of the hypothalamus, the supraoptic nucleus, and the median eminence. Some regions such as the arcuate nucleus, the median eminence, and dorsal hypothalamus exhibit intense labeling of axonal varicosities, while other regions exhibit only perikarya immunolabeling. alpha1B-adrenergic receptor immunoreactivity was also observed in large pyramidal neurons of layer V of the cerebral cortex, the frontal cortex showing a particularly strong immunoreactivity. Virtually all thalamic regions were labeled, especially the lateral and ventral areas. In addition, labeled cells were present in hippocampus, the medial septum, the horizontal and vertical limbs of the diagonal band of Broca, and the caudate putamen. Finally, some midbrain and hindbrain regions important for motor function were immunoreactive. Because ligands specific for alpha1-adrenergic receptor subtypes are not available, the present immunocytochemical study not only addresses the subcellular and regional distribution of alpha1B-adrenergic receptors but may also provide clues about receptor subtype-specific function.     

The metabolic effects of oxytocin are mediated by a uterine type of receptor and are inhibited by oxytocin antagonist and by arginine vasopressin in the dog.

Infusion of oxytocin (OT) into normal dogs, in doses which produced plasma levels of OT in the physiological range, has been shown to increase plasma levels of glucose, insulin and glucagon and increase rates of glucose production and uptake. This study sought to determine whether there was a correlation between these metabolic effects and the oxytocic potency of four less potent oxytocic analogues when infused into normal dogs. The rank order of oxytocic potency of all 4 correlated well with the rise in plasma glucose levels, and in 3 of the 4 with the rise in plasma insulin levels. An antagonist of the oxytocic effect of OT suppressed the usual OT-induced rise in plasma glucose, insulin and glucagon as well as the increased glucose production and uptake. Arginine vasopressin (AVP) infusion, which by itself did not produce any metabolic effects, blocked completely the effects of OT infusion to raise plasma glucose and insulin levels and increase glucose production and uptake. The data suggest that the metabolic effects of OT in the dog are mediated by OT receptors that are similar to those producing the oxytocic effects. Whether the inhibition by AVP of the metabolic and hormonal effects of OT occurs at the receptor or post receptor level or via other mechanisms remains to be determined.     

Development of oxidative stress and cell damage in the liver of rats with water-immersion restraint stress

We examined how oxidative stress and cell damage develop in the liver of rats subjected to water-immersion stress (WIRS). In rats subjected to WIRS for 1.5, 3 or 6 h, serum alanine aminotransferase and aspartate aminotransferase activities increased time-dependently. In the liver tissue, vacuolization and apoptosis occurred at 1.5 h of WIRS and vacuolization further developed without further appearance of apoptosis at 3 h or 6 h. Serum lipid peroxide (LPO) and NOx (nitrite/nitrate) concentrations increased at 3 h of WIRS and these increases were enhanced at 6 h. In liver tissue, increases in LPO and NOx concentrations and myeloperoxidase activity and decreases in ascorbic acid and reduced glutathione concentrations and superoxide dismutase activity occurred at 3 h of WIRS and these changes were enhanced at 6 h, although vitamin E concentration and xanthine oxidase activity were unchanged. These results indicate that oxidative stress in the liver of rats with WIRS develops after the appearance of cell damage in the tissue, and suggests that oxidative stress is caused through disruption of the antioxidant defense system and increases in NO generation and neutrophil infiltration in the liver, which may contribute to the progression of cell damage in the tissue.     

Oxytocin biotransformation in the rat limbic brain: chemical characterization of two oxytocin fragments and proposed pathway for oxytocin conversion

Two peptide fragments of oxytocin were isolated by high-pressure liquid chromatography from digests of oxytocin obtained after exposure to a SPM preparation of the rat limbic brain. The structures of these peptides, being Gln-Asn-Cys(O)_x-Pro-Leu-GlyNH₂ and Gln-Asn-Cys(-S-S-Cys)-Pro-Leu-GlyNH₂, were assessed by quantitative amino acid analysis, combined with the determination of N-terminal end groups and cysteic acid residues after performic acid treatment. The fragments comprised the 4–9 and 1,4–9 sequences of oxytocin, respectively. The types of proteolytic enzymes involved in their formation are discussed and a pathway for the conversion of oxytocin by SPM is proposed.     

催产素和加压素与应激的关系

催产素和加压素是由下丘脑视上核和室旁核大细胞性神经内分泌细胞合成和分泌的一种神经垂体激素。各种应刺激都可以引起催产素和加压素神经元的活动。目前应激后引起的这类神经活动的变化与人类的某结疾病的病理生理相关联正在引起人们的关注。西文总结了近几年在这方面的研究进展。主要内容包括：（1）催产素和加压素神经元在应激中的反应;（2）在大细胞性催产素和加压素神经元的应激反应相关联的神经传递物质;（3）与应激相关联的精神疾病的关系。     

Oxytocin receptor and vasopressin receptor 1a genes are respectively associated with emotional and cognitive empathy

Empathy is the ability to recognize and share in the emotions of others. It can be considered a multifaceted concept with cognitive and emotional aspects. Little is known regarding the underlying neurochemistry of empathy and in the current study we used a neurogenetic approach to explore possible brain neurotransmitter pathways contributing to cognitive and emotional empathy. Both the oxytocin receptor (OXTR) and the arginine vasopressin receptor 1a (AVPR1a) genes contribute to social cognition in both animals and humans and hence are prominent candidates for contributing to empathy. The following research examined the associations between polymorphisms in these two genes and individual differences in emotional and cognitive empathy in a sample of 367 young adults. Intriguingly, we found that emotional empathy was associated solely with OXTR, whereas cognitive empathy was associated solely with AVPR1a. Moreover, no interaction was observed between the two genes and measures of empathy. The current findings contribute to our understanding of the distinct neurogenetic pathways involved in cognitive and emotional empathy and underscore the pervasive role of both oxytocin and vasopressin in modulating human emotions.     

Tetrahydroquinoline sulfonamides as vasopressin 1b receptor anatgonists

Vasopressin 1b (V1b) antagonists have been postulated as possible treatments for depression and anxiety. A novel series of potent and selective V1b antagonists has been identified starting from an in-house screen hit. The incorporation of a sulfonamide linker between a tetrahydroisoquinoline core and amino piperidine lead to the identification of a V1b antagonist with similar affinity for human and rat receptors. Further optimization of the right hand portion afforded potent V1b antagonists that possessed moderate to high selectivity over other receptors.     

V1-receptor mediated GSH efflux by vasopressin from rat hepatocytes.

Vasopression increases sinusoidal efflux of GSH in the perfused rat liver. The mechanism of this effect was studied in the perfused rat liver and in isolated rat hepatocytes. Vasopressin stimulated GSH efflux in both systems and a V1-receptor antagonist (OPC-21268) significantly inhibited the effect of vasopressin suggesting that vasopressin stimulates GSH efflux from rat hepatocytes via V1-receptor.     

Social dominance in male vasopressin 1b receptor knockout mice

We have previously reported that mice with a targeted disruption of their vasopressin 1b receptor gene, Avpr1b, have mild impairments in social recognition and reduced aggression. The reductions in aggression are limited to social forms of aggression, i.e., maternal and inter-male aggression, while predatory aggression remains unaffected. To further clarify the role of the Avpr1b in the regulation of social behavior we first examined anxiety-like and depression-like behaviors in Avpr1b knockout (Avpr1b −/−) mice. We then went on to test the ability of Avpr1b −/− mice to form dominance hierarchies. No major differences were found between Avpr1b −/− and wildtype mice in anxiety-like behaviors, as measured using an elevated plus maze and an open field test, or depression-like behaviors, as measured using a forced swim test. In the social dominance study we found that Avpr1b −/− mice are able to form dominance hierarchies, though in early hierarchy formation dominant Avpr1b −/− mice display significantly more mounting behavior on Day 1 of testing compared to wildtype controls. Further, non-socially dominant Avpr1b −/− mice spend less time engaged in attack behavior than wildtype controls. These findings suggest that while Avpr1b −/− mice may be able to form dominance hierarchies they appear to employ alternate strategies.     

Intra- and extrahypothalamic vasopressin and oxytocin pathways in the rat

Summary Perfusion of rat brain followed by immersion fixation with 2.5% glutaraldehyde-1% paraformaldehyde, purification of the first antisera and application of the unlabelled antibody enzyme method were used to specifically identify vasopressin and oxytocin containing cells and fibres. The conventional sites of production of these hormones were confirmed as follows: supraoptic and paraventricular nuclei, suprachiasmatic nucleus (only vasopressin), and other cells and cell groups of the hypothalamus. Fibres from the suprachiasmatic nucleus spread out in various directions, and probably project to the nucleus praeopticus periventricularis, organum vasculosum laminae terminalis and in the direction of the supraoptic nucleus. Oxytocin and vasopressin containing pathways could be traced from the paraventricular nucleus to the lateral ventricle, the stria terminalis and the stria medullaris. Some of the oxytocin and vasopressin containing tracts appear to continue onto the septum. The possible importance of these morphological findings for the behavioural effects of vasopressin and oxytocin is discussed.The authors wish to thank Dr. L. Sternberger for his generous gift of peroxidase-antiperoxidase complex, and Miss M.M. Smidt, Mr. A. Potjer and Mr. P. Wolters for their assistance. This work was supported in part by the Foundation for Medical Research FUNGO     

Oxytocin,oxytocin-associated neurophysin and the oxytocin receptor in the human prostate

Oxytocin has been implicated in the regulation of prostate growth. However, the cellular localisation of oxytocin in the normal and diseased human prostate is not known. Oxytocin, oxytocin-associated neurophysin and oxytocin receptor were detected by immunohistochemistry in tissues from patients undergoing routine prostatectomy and in normal human prostate epithelial and stromal cell lines. Western blot analysis detected a single band at 14 kDa with neurophysin antiserum and a 66-kDa band with oxytocin receptor antiserum in epithelial and stromal cell lines. Similar sized bands were also detected in extracts of hyperplastic and adenocarcinomic prostate tissues. Oxytocin, oxytocin-associated neurophysin and oxytocin receptor were present in stromal and epithelial cell lines and in tissue from patients with benign prostatic hyperplasia. The peptides were localised predominantly to the epithelial cells, although discrete areas of stromal staining were also observed. There was a significant difference in the intensity of oxytocin-staining between tissue displaying benign prostatic hyperplasia and invasive carcinoma, with less immunoreactivity being present in the malignant epithelial cells. Thus, oxytocin and its neurophysin and receptor are present in epithelial and stromal cells of the human prostate. Oxytocin expression is reduced with tumour progression and may provide a marker for invasive disease.This work was supported by a Project Grant (007756) from the Wellcome Trust and from Lottery Health Research     

Stimulation of rat pituitary phospholipid methyltransferase by vasopressin but not oxytocin

Rat pituitary extracts contain two methyltransferases that catalyze stepwise methylation of phosphatidyl-ethanolamine to phosphatidylcholine using S-adenosylmethionine as the methyl donor. The activities of both of these enzymes were stimulated by 40 μM lysine or arginine vasopresin but not oxytocin, arginine vasotocin and Pro-Leu-Gly NH₂. The concentration of lysine-vasopressin required for the half-maximal stimulation of phospholipid methylation was 27 μM. A comparison of the chemical structure of different peptides with their ability to stimulate phospholipid methylation suggests that the stimulatory activity resides in the covalent ring structure (pressinoic acid) of the vasopressin molecule.     

Ontogeny of vasopressin and oxytocin in the fetal rat: Early vasopressinergic innervation of the fetal brain

The content and distribution of vasopressin and oxytocin were determined during fetal development in the rat brain and pituitary by means of radioimmunoassay and immunocytochemistry. The vasopressin content in the fetal brain showed a gradual rise from day 16 of pregnancy onwards, while pituitary vasopressin rapidly increased from fetal day 19 until birth. The oxytocin content in the fetal brain was considerably lower than the vasopressin content. A decrease in oxytocin content was seen between day 16 and day 18 while from day 18 of pregnancy onwards a slight increase was found. The pituitary oxytocin content starts to rise between day 17 and 18 of pregnancy, but at term the pituitary oxytocin content was only 1/20 of the vasopressin value. Immunocytochemistry revealed that vasopressin levels in the fetal rat brain were not only due to the presence of the classical hypothalamoneurohypophyseal system, but also to the early development of exohypothalamic fibers. Vasopressin containing cells were seen from fetal day 16 in the supraoptic nucleus, and from fetal day 18 in the paraventricular nucleus. The fiber outgrowth of these cells towards the pituitary and extrahypothalamic brain sites seems to be well synchronized, as on day 17 vasopressin containing fibers could be demonstrated in the olfactory bulb as well as in the median eminence. No positive staining for oxytocin could be obtained in the fetal rat, while during the entire fetal period no positive staining was found in cell bodies in the region of the suprachiasmatic nucleus. The early peptidergic innervation of the brain, which enabled the tracing of the source of some exohypothalamic fibers, might be related to several central processes among which brain development itself is included.