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

The effects of activation of metabotropic glutamate receptors (mGluRs) on synaptic inputs to magnocellular neurons of the hypothalamic supraoptic nucleus (SON) were studied with the use of whole cell patch-clamp and microelectrode recordings in acute hypothalamic slices. Application of the mGluR agonist trans-(+/-)-1-amino-1,3-cyclopentane dicarboxylic acid (trans-ACPD, 100 microM) elicited an increase in the frequency of spontaneous excitatory postsynaptic potentials (EPSPs) and excitatory postsynaptic currents (EPSCs) in 20% of the cells, and of spontaneous inhibitory postsynaptic potentials (IPSPs) and inhibitory postsynaptic currents (IPSCs) in 50% of the cells tested in normal medium. The increased frequency of spontaneous EPSPs/EPSCs and IPSPs/IPSCs was blocked by tetrodotoxin (TTX), indicating that mGluRs act to excite the somata/dendrites of presynaptic glutamatergic and GABAergic neurons. (RS)-3,5-dihydroxyphenylglycine (50 microM), a selective group I receptor agonist, mimicked the presynaptic somatic/dendritic effects of trans-ACPD, suggesting that the presynaptic somatic/dendritic receptors responsible for increased spike-dependent glutamate and gamma-aminobutyric acid (GABA) release belong to the group I mGluRs. In the presence of TTX, trans-ACPD caused a decrease in the frequency of miniature EPSCs (up to 90%) in 13 of 16 cells, and a decrease in the frequency of miniature IPSCs (up to 80%) in 10 of 16 cells tested. Miniature EPSC and IPSC amplitudes usually did not change in trans-ACPD, suggesting that activation of metabotropic receptors located at presynaptic glutamatergic and GABAergic terminals led to a reduction in transmitter release onto SON magnocellular neurons. L(+)-2-amino-4-phosphonobutyric acid (100-250 microM), a selective group III receptor agonist, mimicked the effects of trans-ACPD at presynaptic terminals, decreasing the frequency of miniature EPSCs and IPSCs by up to 85% without affecting their amplitude. Thus the metabotropic receptors at presynaptic glutamate and GABA terminals in the SON belong to group III mGluRs. EPSCs evoked by electrical stimulation were enhanced by the group III receptor antagonist (S)-2-amino-2-methyl-4-phosphonobutanoic acid, suggesting that presynaptic metabotropic receptors are activated by the release of endogenous glutamate. These data indicate that mGluRs in the hypothalamus have opposing actions at presynaptic somata/dendrites and at presynaptic terminals. Activation of group I receptors (mGluR1 and/or mGluR5) on presynaptic somata/dendrites led to an increase in spike-dependent transmitter release, whereas activation of the group III receptors (mGluR4, 7, and/or 8) on presynaptic terminals suppressed glutamate and GABA release onto SON neurons. No differences were seen in the effects of mGluR activation between immunohistochemically identified oxytocin and vasopressin neurons of the SON.
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PMID:Presynaptic modulation by metabotropic glutamate receptors of excitatory and inhibitory synaptic inputs to hypothalamic magnocellular neurons. 906 26

We studied the effects of activation of the metabotropic glutamate receptors on intrinsic currents of magnocellular n urons of the supraoptic nucleus (SON) with whole cell patch-clamp and conventional intracellular recordings in coronal slices (400 micron) of the rat hypothalamus. Trans-(+/-)-1-amino-1,3-cyclopentane dicarboxylic acid (trans-ACPD, 10-100 microM), a broad-spectrum metabotropic glutamate receptor agonist, evoked an inward current (18.7 +/- 3.45 pA) or a slow depolarization (7.35 +/- 4.73 mV) and a 10-30% decrease in whole cell conductance in approximately 50% of the magnocellular neurons recorded at resting membrane potential. The decrease in conductance and the inward current were caused largely by the attenuation of a resting potassium conductance because they were reduced by the replacement of intracellular potassium with an equimolar concentration of cesium or by the addition of potassium channel blockers to the extracellular medium. In some cells, trans-ACPD still elicited a small inward current after blockade of potassium currents, which was abolished by the calcium channel blocker, CdCl2. Trans-ACPD also reduced voltage-gated and Ca2+-activated K+ currents in these cells. Trans-ACPD reduced the transient outward current (IA) by 20-70% and/or the IA-mediated delay to spike generation in approximately 60% of magnocellular neurons tested. The cells that showed a reduction of IA generally also showed a 20-60% reduction in a voltage-gated, sustained outward current. Finally, trans-ACPD attenuated the Ca2+-dependent outward current responsible for the afterhyperpolarization (IAHP) in approximately 60% of cells tested. This often revealed an underlying inward current thought to be responsible for the depolarizing afterpotential seen in some magnocellular neurons. (RS)-3,5-dihydroxyphenylglycine, a group I receptor-selective agonist, mimicked the effects of trans-ACPD on the resting and voltage-gated K+ currents. (RS)-alpha-methyl-4-carboxyphenylglycine, a group I/II metabotropic glutamate receptor antagonist, blocked these effects. A group II receptor agonist, 2S,1'S,2'S-2carboxycyclopropylglycine and a group III receptor agonist, (+)-2-amino-4-phosphonobutyric acid, had no effect on the resting or voltage-gated K+ currents, indicating that the reduction of K+ currents was mediated by group I receptors. About 80% of the SON cells that were labeled immunohistochemically for vasopressin responded to metabotropic glutamate receptor activation, whereas only 33% of labeled oxytocin cells responded, suggesting that metabotropic receptors are expressed preferentially in vasopressinergic neurons. These data indicate that activation of the group I metabotropic glutamate receptors leads to an increase in the postsynaptic excitability of magnocellular neurons by blocking resting K+ currents as well as by reducing voltage-gated and Ca2+-activated K+ currents.
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PMID:Modulation of multiple potassium currents by metabotropic glutamate receptors in neurons of the hypothalamic supraoptic nucleus. 940 56

To provide a simple means to isolate and study the cellular functions of small groups of neurons, we developed a modified 'punch' culture procedure that facilitates acute and long-term in vitro physiological studies. Primary 'punch' cultures of magnocellular neuroendocrine cells (MNCs) from the supraoptic nucleus (SON) were established and the basic physiological effects of subtype-specific glutamate receptor agonists were characterized. MNCs from the punch cultures established a mature morphology in culture with extensive outgrowth of axons and varicosities. After 8 days, a single cultured SON punch produced an average of 10.0 +/- 2.1 pg AVP and contained an average of 222 +/- 53 vasopressin-neurophysin immunoreactive cells. Patch clamp recordings from MNCs demonstrated the presence of N-methyl-D-aspartate (NMDA)-sensitive and DL, alpha-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA)-receptors. Stimulation of metabotropic receptors with 1S,3R ACPD induced acute or gradual increases in intracellular calcium. NMDA, AMPA and metabotropic receptors all contributed to the secretion of vasopressin from the punch cultures with an agonist rank order potency of: NMDA (10 microM) > AMPA (1 microM) = 1S,3R ACPD (100 microM) > kainate (10 microM). This culture preparation should be useful for cellular studies of small groups of neuroendocrine and other cells.
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PMID:Functional activation of punch-cultured magnocellular neuroendocrine cells by glutamate receptor subtypes. 1047 84

The effect of metabotropic glutamate receptor (mGluR) activation on vasopressin (VP) and oxytocin (OT) release was evaluated using explants of the hypothalamoneurohypophysial system. (+/-)-1-Aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD), an agonist at groups I and II mGluRs, increased VP and OT release in a concentration-dependent manner. A role for group I mGluRs in VP and OT release was demonstrated by the ability of a group I-specific mGluR antagonist, 1-aminoindan-1,5-idicarboxylic acid (AIDA), to block the effect of t-ACPD and the ability of a group I-specific agonist, (R,S)-3,5-dihydroxyphenylglycine, to significantly increase both VP (P = 0.0029) and OT (P = 0.0032) release. However, AIDA did not alter VP or OT release induced by a ramp increase in osmolality of the perifusion medium. The role of group III mGluRs was examined using L(+)-2-amino-4-phosphonobutyric acid (L-AP4), an agonist of these receptors. L-AP4 did not change basal release of VP or OT and did not prevent osmotically stimulated hormone release. Thus mGluR activation stimulates VP and OT release, but it is not required for osmotic stimulation of hormone release.
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PMID:Role of metabotropic glutamate receptors in vasopressin and oxytocin release. 1144 47

In order to determine whether ionotropic (iGluRs) and metabotropic (mGluRs) glutamate receptor activation modulates oxytocin release in male rats, we investigated the effect of agonists of both types of glutamate receptors on oxytocin release from hypothalamus and posterior pituitary. Kainate and quisqualate (1 mM) increased hypothalamic oxytocin release. Their effects were prevented by selective AMPA/kainate receptor antagonists. NMDA (0.01-1 mM) did not modify hypothalamic oxytocin release. Group I mGluR agonists, such as quisqualate and 3-HPG, significantly increased hypothalamic oxytocin release. These effects were blocked by AIDA (a selective antagonist of group I mGluRs). In the posterior pituitary, oxytocin release was not modified by kainate, quisqualate, trans-ACPD (a broad-spectrum mGluR agonist) and L-SOP (a group III mGluR agonist). However, NMDA (0.1 mM) significantly decreased oxytocin release from posterior pituitary. D-Aspartate significantly increased oxytocin release from the hypothalamus, while it decreased oxytocin release from posterior pituitary. AP-5 (a specific NMDA receptor antagonist) reduced the D-Aspartate effect in the hypothalamus, but not in the posterior pituitary. Our data indicate that the activation of non-NMDA receptors and group I mGluRs stimulates oxytocin release from hypothalamic nuclei, whereas NMDA inhibits oxytocinergic terminals in the posterior pituitary. D-Aspartate also has a dual effect on oxytocin release: stimulatory at the hypothalamus and inhibitory at the posterior pituitary. These results suggest that excitatory amino acids differentially modulate the secretion of oxytocin at the hypothalamic and posterior pituitary levels.
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PMID:Differential effects of glutamate agonists and D-aspartate on oxytocin release from hypothalamus and posterior pituitary of male rats. 1176 5