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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vasopressin and oxytocin neuroendocrine cells within the supraoptic nucleus display distinctive electrophysiological properties and differential responses to selected NMDA receptor (NR) antagonists. To determine if these differences might be due to NMDA receptor composition, we compared the expression of NR1, NR2A, NR2B, NR2C and NR2D subunit mRNAs in immunocytochemically identified vasopressin and oxytocin neuroendocrine cells. In contrast to NR1 subunit mRNA which was equally expressed in both vasopressin and oxytocin cells, NR2B and NR2C displayed very different expression patterns. In oxytocin cells, the NR2B subunit comprised the majority (65%) of the total NR2 expression with NR2C and NR2D contributing 6% and 27%, respectively. Vasopressin cells exhibited 5-fold higher NR2C (32%), approximately half as much NR2B mRNA (39%) and equivalent NR2D (31%). In vitro expression studies have shown that the NR1-NR2C subunit combination exhibits weaker magnesium block and higher affinity for glycine than NR1-NR2B. Thus, the high expression of NR2C in vasopressin cells relative to oxytocin cells may make these cells more susceptible to glutamatergic activation. These observations in vasopressin and oxytocin cells provide the basis for a working model to investigate how differential NMDA receptor composition may shape the neurophysiological properties of neurons.
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PMID:Differential expression of five N-methyl-D-aspartate receptor subunit mRNAs in vasopressin and oxytocin neuroendocrine cells. 907 68

Hypothalamo-neurohypophysial magnocellular neurons display specific electrical activities in relation to the mode of release of their hormonal content (vasopressin or oxytocin). These activities are under strong glutamatergic excitatory control. The implication of NMDA receptors in the control of vasopressinergic and oxytocinergic neurons is still a matter of debate. We here report the first detailed characterization of functional properties of NMDA receptors in voltage-clamped magnocellular neurons acutely dissociated from the supraoptic nucleus. All cells responded to NMDA with currents that reversed polarity around 0 mV and were inhibited by D-2-amino-5-phosphonovalerate (D-APV) and by 100 microM extracellular Mg2+ (at -80 mV). Sensitivity to the co-agonist glycine (EC50, 2 microM) was low compared with most other neuronal preparations. The receptors displayed low sensitivity to ifenprodil, were insensitive to glycine-independent potentiation by spermine, and had a unitary conductance of 50 pS. No evidence was found for two distinct cell populations, suggesting that oxytocinergic and vasopressinergic neurons express similar NMDA receptors. Characterization of NMDA receptors at different postnatal ages revealed a transient increase in density of NMDA currents during the second postnatal week. This was accompanied by a specific decrease in sensitivity to D-APV, with no change in NMDA sensitivity or any other properties studied. Supraoptic NMDA receptors thus present characteristics that strikingly resemble those of reconstituted receptors composed of NR1 and NR2A subunits. Understanding the functional significance of the development of NMDA receptors in the supraoptic nucleus will require further knowledge about the maturation of neuronal excitability, synaptic connections and neurohormone release mechanisms.
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PMID:NMDA receptor properties in rat supraoptic magnocellular neurons: characterization and postnatal development. 924 Apr 1

Vasopressin and oxytocin neuroendocrine cells within the supraoptic nucleus of the adult hypothalamus (SON) display mRNA expression for the NMDA receptor subunits, NR1 and NR2B, NR2C and NR2D. The NR2B subunit confers slow decay kinetics (relative to NR1/NR2A receptors) and high magnesium sensitivity to NMDA receptor responses--properties which may contribute to the NMDA receptor-mediated bursting manifested by these cells. Therefore, we examined NR2B protein expression and its developmental profile in the SON and compared it to that in the cortex and cerebellum--areas which have been studied previously. We performed Western blot analysis on SON homogenates from embryonic, postnatal (PN7, 14, 21), and adult rats using an NR2B-specific antibody. Adult NR2B levels in the SON and PVN were similar but low relative to those of cortex. SON NR2B protein levels rose in the first postnatal week, remained high through PN21, and later declined to significantly lower levels in the adult. A similar profile was observed in cerebellum, where NR2B expression displayed a sharp peak at PN14 and later declined to minimal or undetectable levels in the adult. In contrast, NR2B continued to be overexpressed through adulthood in the cortex. The ontogenic pattern for NR1 expression, which included unregulation during early postnatal life and adulthood, was similar in the SON and cortex. A different pattern was observed for the cerebellum, where NR1 levels increased gradually after ED17 to reach significantly greater adult levels. Of all three areas studied, the SON displayed the earliest developmental rise in NR1 levels. SON explant cultures proved to be a useful preparation, since they contained neurons which synthesized NR1 and NR2B subunits in quantities similar to those of ED17 SON. Our findings suggest that NMDA receptors on SON neuroendocrine cells are assembled using NR1 and NR2B subunits, and that their plastic expression in early postnatal life may play a role during development.
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PMID:Developmental plasticity of NR1 and NR2B subunit expression in the supraoptic nucleus of the rat hypothalamus. 970 87

Present experiments in rats were aimed to verify the hypothesis that glutamatergic neurotransmission and stress hormones play a role in impairment of hedonic behavior, a sign of depression-like state. On the basis of individual variability in sucrose preference, test rats were divided into anhedonic and hedonic groups. Anhedonic animals showed higher basal concentrations of adrenocorticotropin and corticosterone but reduced hormonal responses during novelty stress compared to hedonic animals. Acute administration of citalopram (10 mg/kg ip) induced similar effects in both groups. Corticotropin-releasing hormone (CRH) mRNA levels in hypothalamic paraventricular nucleus (PVN) were higher in anhedonic rats. Oxytocin (OT) and vasopressin gene expression in the PVN and proopiomelanocortin (POMC) expression in the anterior pituitary failed to show any significant differences. Gene expression of NR1 receptor subunit of N-methyl-D-aspartate (NMDA) glutamate receptor in the ventral tegmental area (VTA) was found to be lower in anhedonic rats. In the nucleus accumbens (NAc) and the hippocampus of anhedonic animals, higher mRNA levels of NR2A subunit compared to those of hedonic rats were detected. Thus, low sucrose preference is associated with altered HPA axis activity, NMDA receptor subunits and CRH gene expression in selected brain regions. These mechanisms may operate in the disposition to develop hedonic deficit in some mental disorders.
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PMID:Altered glutamate receptor and corticoliberin gene expression in brain regions related to hedonic behavior in rats. 1367 12

The supraoptic nucleus (SON) of the hypothalamus contains magnocellular neurosecretory neurons (MNC) which synthesize and release the peptide hormones vasopressin and oxytocin. Glutamate is a prominent excitatory neurotransmitter in the SON and regulates MNC excitability. NMDA receptors (NMDAR), a type of ionotropic glutamate receptor, mediate synaptic plasticity of MNCs and are necessary for characteristic burst firing patterns which serve to maximize hormone release. NMDARs are di- or tri-heteromeric complexes of NR1 and NR2 subunits. Receptor properties depend on NR2 subunit composition and variable splicing of NR1. We investigated the expression profile of NR1 and NR2 subunits in the SON at the mRNA and protein levels plus protein expression of NR1 splice variants in control and salt-loaded adult rats. There was robust mRNA expression of all subunits, with NR2D levels being the highest. At the protein level, NR1, NR2B, and NR2D were robustly expressed, while NR2A was weakly expressed. NR2C protein was not detected with either of the two antibodies tested. All four NR1 splice variant cassettes (N1, C1, C2, C2') were detected in the SON, although NR1 N1 expression was too low for accurate analysis. Three days of salt-loading did not alter mRNA, protein, or splice variant expression of NMDAR subunits in the SON. Robust NR2D protein expression has not been previously shown in MNCs and is uncommon in the adult brain. Although the functional significance of this unusual expression profile is unknown, it may contribute to important physiological characteristics of SON neurons, such as burst firing and resistance to excitotoxicity.
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PMID:NMDA receptor subunit expression in the supraoptic nucleus of adult rats: dominance of NR2B and NR2D. 2139 92

The ability to learn and remember conspecifics is essential for the establishment and maintenance of social groups. Many animals, including humans, primates and rodents, depend on stable social relationships for survival. Social learning and social recognition have become emerging areas of interest for neuroscientists but are still not well understood. It has been established that several hormones play a role in the modulation of social recognition including estrogen, oxytocin and arginine vasopression. Relatively few studies have investigated how social recognition might be improved or enhanced. In this study, we investigate the role of the NMDA receptor in social recognition memory, specifically the consequences of altering the ratio of the NR2B:NR2A subunits in the forebrain regions in social behavior. We produced transgenic mice in which the NR2B subunit of the NMDA receptor was overexpressed postnatally in the excitatory neurons of the forebrain areas including the cortex, amygdala and hippocampus. We investigated the ability of both our transgenic animals and their wild-type littermate to learn and remember juvenile conspecifics using both 1-hr and 24-hr memory tests. Our experiments show that the wild-type animals and NR2B transgenic mice preformed similarly in the 1-hr test. However, transgenic mice showed better performances in 24-hr tests of recognizing animals of a different strain or animals of a different species. We conclude that NR2B overexpression in the forebrain enhances social recognition memory for different strains and animal species.
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PMID:genetic overexpression of NR2B subunit enhances social recognition memory for different strains and species. 2255 58