Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Olfactory bulbectomized (OBX) rats show a variety of behavioral and biochemical deficits that parallel human depression. We investigated the expression of glutamate receptor subtypes in cortical and subcortical brain regions following bilateral olfactory bulbectomy in adult rats. Quantitative receptor autoradiography using [(125)I]MK-801 (NMDA receptor), [(3)H]AMPA (AMPA receptor), and [(3)H]kainate (kainate receptor) was performed on brain sections at 1-5 weeks following olfactory bulbectomy. Our results show an elevation of NMDA receptors in the medial prefrontal cortex within 1 week following bulbectomy, which persisted up to at least 5 weeks post-bulbectomy. Neither kainate nor AMPA receptors were altered in any brain region examined. The potential significance of these results is discussed in light of experimental findings supporting a role for NMDA receptors in the mechanism of action of antidepressant drugs and the pathophysiology of major depression.
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PMID:Olfactory bulbectomy alters NMDA receptor levels in the rat prefrontal cortex. 1088 Oct 36

Hypoglutamatergic function is implicated in the pathogenesis of schizophrenia, and supersensitivity of platelet NMDA receptors has been reported in schizophrenia. The aim of this study was to examine the platelet glutamate receptor sensitivity in patients with schizophrenia (n=12), mania with psychotic features (n=10) and depression with psychotic features (n=10) and matched controls (n=12) in order to assess if this is a marker of schizophrenia or occurs in other psychotic conditions. Glutamate receptor sensitivity was assessed using the intracellular calcium response to glutamate measured with spectrofluorometry. The percentage response of the schizophrenic and depressed psychotic subjects to glutamate stimulation was significantly greater than control subjects (p<0.005). The mania with psychotic features group was not significantly different to controls. This data suggests that platelet glutamate receptors may be supersensitive in schizophrenia and depression with psychotic features. Furthermore, the platelet may be a possible peripheral marker of glutamate function in schizophrenia and depression with psychotic features.
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PMID:The specificity of platelet glutamate receptor supersensitivity in psychotic disorders. 1089 85

To investigate the mechanism of chronic cell death following postischemic hypothermia, the change of N-methyl-D-aspartate receptor (NMDAR) were examined by immunohistochemistry of NMDAR1 and long-term potentiation (LTP) in the CA1 subfield of the gerbil hippocampus. At 1 week following postischemic hypothermia (32 degrees Cx4 h), all CA1 neurons survived; however, immunoreactivity of NMDAR1 increased in neuronal perikarya whereas decreased in dendrites in the CA1 neurons. The abnormality was still observed in remaining CA1 neurons at 1 month after hypothermia. LTP was also significantly depressed at 1 week after hypothermia. These results suggest that some abnormalities in the glutamate receptor may be caused by ischemia; such abnormality would persist in spite of hypothermia treatment, resulting in the depression of LTP.
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PMID:Depression of long term potentiation in gerbil hippocampus following postischemic hypothermia. 1091 27

We have previously provided functional evidence that glycine and GABA are contained in the same synaptic vesicles and coreleased at the same synapses in lamina I of the rat spinal dorsal horn. However, whereas both glycine receptors (GlyRs) and GABA(A) receptors (GABA(A)Rs) are expressed on the postsynaptic target, under certain conditions inhibitory events appeared to be mediated by GlyRs only. We therefore wanted to test whether GABA(B) receptors could be activated in conditions where GABA released was insufficient to activate GABA(A)Rs. Focal stimulation in the vicinity of visually identified lamina I neurons elicited monosynaptic IPSCs in the presence of ionotropic glutamate receptor antagonists. Pairs of stimuli were given at different interstimulus intervals (ISI), ranging from 25 ms to 1 s to study the depression of the second of evoked IPSCs (paired pulse depression; PPD). Maximal PPD of IPSCs was 60 +/- 14% (SE) (of the conditioning pulse amplitude), at ISI between 150 and 200 ms. PPD was observed with IPSCs evoked at stimulus intensities where they had no GABA(A)R component. PPD of small evoked IPSCs was not affected by the GABA(A)R antagonist bicuculline but significantly attenuated by 10-30 microM CGP52432, a specific GABA(B) receptor antagonist. These data indicate that, under conditions where GABA released is insufficient to affect postsynaptic GABA(A)Rs at lamina I inhibitory synapses, significant activation of presynaptic GABA(B) receptors can occur.
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PMID:GABA(B) receptors are the first target of released GABA at lamina I inhibitory synapses in the adult rat spinal cord. 1093 23

Endogenous adenosine, acting upon A(1) receptors, attenuates long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission in hippocampal slices. Adenosine might exert these effects by inhibiting the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor. Theta burst-induced LTP was larger in the presence of the selective adenosine A(1) receptor antagonist, 1, 3-dipropyl-8-cyclopentylxanthine (DPCPX, 50nM, 40.5+/-6.6% increase in fEPSP) than in the control solution (18.2+/-4.7% increase), and was completely prevented in the presence of DPCPX (50nM) plus the selective NMDA receptor antagonist, DL-2-amino-5-phosphonopentanoate (AP5, 50microM, -3.3+/-7.0% change). In contrast, LTD was induced by low-frequency stimulation in the presence of DPCPX (50nM), even in experiments performed in AP5 (50microM). Thus LTP, but not LTD, observed upon blockade of adenosine A(1) receptors is dependent upon NMDA receptor activation.
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PMID:Long-term potentiation observed upon blockade of adenosine A1 receptors in rat hippocampus is N-methyl-D-aspartate receptor-dependent. 1097 79

The effects of N-methyl-D-aspartate (NMDA) glutamate receptor antagonists on the mechanisms of nociceptive sensitization were studied in LPl1 and RPl1 neurons of the semiintact preparation of a Helix lucorum snail. Application of sensitizing stimuli on the head part of the control preparation led to a depolarization of the membrane and increase in its excitability. A depression of responses of neurons evoked by tactile or chemical sensory stimulation during the short-term period and significant facilitation of responses during the long-term period of sensitization were observed. Sensitization performed under conditions of application of NMDA antagonists (AP5 or MK801) produced similar changes in membrane potential, membrane excitability, and neuronal responses evoked by tactile stimulation of the head or foot. However, the chemical stimulation of the head under these conditions evoked a significant depression of responses during the short- and long-term sensitization periods. The results suggest that the NMDA glutamate receptor antagonists selectively affect the plasticity induction mechanisms of the command neuron synaptic inputs, which mediate the chemical sensory stimulation from the snail's head.
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PMID:[Antagonists of NMDA glutamate receptors selectively affect synaptic mechanisms of the nociceptive sensitization in the snail]. 1098 13

The history of pharmacological examinations of glutamate receptor agonists such as kainic acid, quisqualic acid, acromelic acid, L-CCG-I, DCG-IV and L-F2CCG-I was described. Kainic acid is one of the most potent excitants in the mammalian central neurons, and its powerful excitatory actions gave rise to the excitotoxic concept that glutamate destroys neurons by excessive activation of excitatory receptors. Single systemic administration of acromelic acid, a kainate analog, caused behavioral and pathological effects quite different from those seen after systemic administration of kainate in the rat, demonstrating that the distribution of neuron damage caused by various excitatory amino acids is not always identical even if their receptors are in the same pharmacological category. 2-(Carboxycyclopropyl)glycine (CCG) is a conformationally restricted analogue of glutamate. CCG and its derivatives demonstrate unique neuropharmacological actions; for example, L-CCG-I and DCG-IV (a carboxylated derivative of L-CCG-I) relatively preferentially activate group II mGluRs. Prolonged infusion of very small amounts of DCG-IV showed a bell-shaped dose-response relationship with regard to protection against kainate-induced neurotoxicity. Low concentrations of L-glutamate neither affected spinal reflexes nor the resting membrane potentials of motoneurons, but preferentially potentiated the depression of monosynaptic excitation caused by L-F2CCG-I. Following L-F2 CCG-I treatment, L-glutamate decreased the monosynaptic spinal reflexes in a concentration-dependent manner, indicating a 'priming' effect of L-F2CCG-I. Thus, pharmacological actions of mGluR agonists are of great interest and remain to be clarified.
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PMID:[Pharmacology of the glutamate receptor]. 1103 41

A number of studies indicate that prolonged, major depression is associated with a selective loss of hippocampal volume that persists long after the depression has resolved. This review is prompted by two ideas. The first is that overt neuron loss may be a contributing factor to the decrease in hippocampal volume. As such, the first half of this article reviews current knowledge about how hippocampal neurons die during insults, focusing on issues related to the trafficking of glutamate and calcium, glutamate receptor subtypes, oxygen radical generation, programmed cell death, and neuronal defenses. This is meant to orient the reader toward the biology that is likely to underlie any such instances of neuron loss in major depression. The second idea is that glucocorticoids, the adrenal steroids secreted during stress, may play a contributing role to any such neuron loss. The subtypes of depression associated with the hippocampal atrophy typically involve significant hypersecretion of glucocorticoids, and the steroid has a variety of adverse effects in the hippocampus, including causing overt neuron loss. The second half of this article reviews the steps in this cascade of hippocampal neuron death that are regulated by glucocorticoids.
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PMID:The possibility of neurotoxicity in the hippocampus in major depression: a primer on neuron death. 1106 67

The ability of the antagonists for the N-methyl-D-aspartate (NMDA) type of glutamate receptor to modulate locomotor activity were compared in alcohol-sensitive (or alcohol-nontolerant, ANT) and alcohol-insensitive (or alcohol-tolerant, AT) rat lines. Both rat lines showed altered locomotor activity after acute injections of a competitive antagonist (LY235959), a glycine-site antagonist (L-701,324), or noncompetitive antagonists [MK-801, phencyclidine (PCP), and ketamine] of the NMDA receptor. MK-801 at 0.5 mg/kg caused a strong increase in horizontal activity in both rat lines, the effect being significantly greater in the ANT rats. There was a subpopulation among AT rats that was almost completely unresponsive to MK-801. This insensitivity to MK-801 correlated with the lack of c-fos induction in the retrosplenial and cingulate cortices. Fos immunoreactive cells in these brain regions after MK-801 treatment were more numerous in ANT than AT rats, although c-fos induction in the inferior olivary nucleus was similar in all animals after MK-801. The ANT rats showed greater locomotor stimulation also after ketamine and LY235959, while stimulation induced by PCP and depression induced by L-701,324 did not differ between the rat lines. The data suggest that altered NMDA receptor-mediated processes may correlate with differences in innate alcohol sensitivity in the ANT/AT rat model.
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PMID:Enhanced locomotor stimulation by NMDA receptor antagonists in alcohol-sensitive ANT rats. 1116 70

An important but poorly understood event associated with ischemia is anoxic depolarization (AD), a sudden and profound depolarization of neurons and glia in cortical and subcortical gray matter. Leao first measured the AD as a wave of electrical silence moving across the cerebral cortex in 1947 and noted its similarity to spreading depression (SD). SD is harmless when coursing through normoxic cortical tissue as during migraine aura. However for 3-4 h following focal ischemia, the additional metabolic stress arising from recurring SD in the penumbra expands the ischemic core, so SD blockade is potentially beneficial therapeutically. In the present study, we measured intrinsic optical signals (IOSs) to monitor anoxic depolarization in submerged rat neocortical slices during O2/glucose deprivation (OGD). After approximately 6 min of OGD, the AD was imaged as a focal increase in light transmittance which then propagated across neocortical gray at approximately 2 mm/min. Although the slice was globally stressed, the AD always initiated focally, sometimes at multiple sites. Its propagation was coincident with a transient negative shift in the extracellular potential, the electrical signature of AD. Acute damage to neocortex (measured as a delayed decrease in LT and as a loss of the evoked field potential) followed only where the AD had propagated, so it is the combined metabolic demands of AD and OGD that acutely damages all layers of the neocortex. Glutamate receptor antagonists (2 mM kynurenate or 25 microM AP-5/10 microM CNQX) did not block AD initiation, slow its propagation or prevent post-AD damage. This study shows that acute ischemic damage is greatly exacerberated by AD during metabolic stress and that glutamate receptor antagonists are not protective. Using this slice model, therapeutically tolerable drugs that block the AD and SD can be investigated.
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PMID:Anoxic depolarization mediates acute damage independent of glutamate in neocortical brain slices. 1123 96


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