UMLS:C0848237 - FACTA Search

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Query: UMLS:C0848237 (acute stress)
4,619 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This review covers some recent findings of the electrophysiological mechanisms through which mesocortical dopamine modulates prefrontal cortical neurons. Dopamine has been shown to modulate several ionic conductances located along the soma-dendritic axis of prefrontal cortical pyramidal neurons. These ionic currents include high-voltage-activated calcium currents and slowly inactivating Na+ and K+ currents. They contribute actively in processing functionally segregated inputs during synaptic integration. In addition, dopamine mainly depolarizes the fast-spiking subtype of local GABAergic interneurons that connect the pyramidal neurons. This latter action can indirectly control pyramidal cell excitability. These electrophysiological data indicate that the actions of dopamine are neither "excitatory" nor "inhibitory" in pyramidal prefrontal cortex neurons. Rather, the actions of dopamine are dependent on somadendritic loci, timing of the arrival of synaptic inputs, strength of synaptic inputs, as well as the membrane potential range at which the PFC neuron is operating at a given moment. Based on available electrophysiological findings, a neuronal model of the pathophysiology of schizophrenia is presented. This model proposes that episodic hypo- and hyperactivity of the PFC and the associated dysfunctional mesocortical dopamine system (and their interconnected brain regions) may coexist in the same schizophrenic patient in the course of the illness. We hypothesize that the dysfunctional mesocortical dopamine input to the PFC may lead to abnormal modulation of ionic channels distributed in the dendritic-somatic compartments of PFC pyramidal neurons that project to the ventral tegmental area and/or nucleus accumbens. In some schizophrenics, a reduction of mesocortical dopamine to below optimal levels and/or a loss of local GABAergic inputs may result in a dysfunctional integration of extrinsic associative inputs by Ca2+ channel activity in the distal dendrites of PFC pyramidal neurons. This may account for the patients' distractibility caused by their inability to focus only on relevant external inputs. In contrast, in acute stress or psychotic episodes, an associated abnormal elevation of mesocortical dopamine transmission may greatly influence distal dendritic Ca2+ channel-mediated signal-processing mechanisms. This can enhance possible reverberative activity between adjacent interconnected pyramidal neurons via the effects of dopamine on the slowly inactivating Na+, K+, and soma-dendritic Ca2+ currents. The effects of high levels of PFC dopamine in this case may contribute to behavioral perseveration and stereotypy so that the patients are unable to use new external cues to modify ongoing behaviors.
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PMID:Developing a neuronal model for the pathophysiology of schizophrenia based on the nature of electrophysiological actions of dopamine in the prefrontal cortex. 1043 66

Previous reports have demonstrated reduced elevations of free intracellular calcium concentration in blood cells of depressed patients after various stimuli. Therefore, a disturbance of intracellular calcium (Ca2+) homeostasis has been postulated to be involved in the pathophysiology of mood disorders. It was the aim of the present study to investigate whether Ca2+ signaling was affected in spleen T-lymphocytes of rats submitted to a learned helplessness paradigm, an animal model of depression with a high level of construct, face and predictive validity. In addition, we tested for effects of acute stress on the Ca2+ signaling in helpless rats, as compared to non-stressed rats. It was found that mitogen-induced Ca2+ signaling only tended to be reduced in helpless rats. However, when helpless rats were submitted to acute immobilization stress, Ca2+ signaling appeared to be significantly blunted, whereas the same stressor did not affect Ca2+ signaling in the non-helpless control rats. These acute stress-induced differences in Ca2+ signaling were not paralleled by a differential increase in plasma corticosterone. It is hypothesized that blunted Ca2+ signaling, as assessed in spleen T-lymphocytes of helpless rats, may be a correlate of the increased vulnerability of helpless rats to acute stressors.
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PMID:Acute stress induced modifications of calcium signaling in learned helpless rats. 1095 61

The underlying mechanisms by which physical or psychological stress causes neurodegeneration are still unknown. We have demonstrated that the high-output and long-lasting synthesizing source of nitric oxide (NO), inducible NO synthase (iNOS), is expressed in brain cortex during stress and that its overexpression accounts for the neurodegenerative changes seen after 3 weeks of repeated stress. Now we have found that acute stress (restraint for 6 h) increases the activity of a calcium-independent NOS and induces the expression of iNOS in brain cortex in adult male rats. In order to elucidate the possible mechanisms involved in this induction, we studied the role of transcription nuclear factor kappaB (NF-kappaB), which is required for iNOS synthesis. We have observed that an acute restraint stress session stimulates the translocation of the NF-kappaB to the nucleus after 4 h and that the administration of the NF-kappaB inhibitor pyrrolidine dithiocarbamate [PDTC, 75 and 150 mg/kg intraperitoneally (i.p.)] at the onset of stress inhibits the stress-induced increase in iNOS expression. Since glutamate release and subsequent NMDA (N-methyl-D-aspartate) receptor activation has been recognized as an early change after exposure to stressful stimuli, and glutamate has been shown to induce iNOS in brain via a NF-kappaB-dependent mechanism, we studied the possible role of excitatory amino acids in the induction of iNOS in our model. Pretreatment with the NMDA receptor antagonist dizocilpine (MK-801, 0.1 and 0.3 mg/kg i.p.) inhibits the stress-induced NF-kappaB activation as well as the stress-induced increase in iNOS expression. Taken together, these findings indicate that excitatory amino acids and subsequent activation of NF-kappaB account for stress-induced iNOS expression in cerebral cortex, and support a possible neuroprotective role for specific inhibitors in this situation.
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PMID:Inducible nitric oxide synthase expression in brain cortex after acute restraint stress is regulated by nuclear factor kappaB-mediated mechanisms. 1120 16

In the present experiments, we characterized the action of human/rat corticotropin-releasing factor (h/rCRF) and acute stress (1 hr of immobilization) on hippocampus-dependent learning and on synaptic plasticity in the mouse hippocampus. We first showed that h/rCRF application and acute stress facilitated (primed) long-term potentiation of population spikes (PS-LTP) in the mouse hippocampus and enhanced context-dependent fear conditioning. Both the priming of PS-LTP and the improvement of context-dependent fear conditioning were prevented by the CRF receptor antagonist [Glu(11,16)]astressin. PS-LTP priming and improved learning were also reduced by the protein kinase C inhibitor bisindolylmaleimide I. Acute stress induced the activation of Ca2+/calmodulin-dependent kinase II (CaMKII) 2 hr after the end of the stress session. The CaMKII inhibitor KN-62 antagonized the stress-mediated learning enhancement, however, with no effect on PS-LTP persistence. Thus, long-lasting increased neuronal excitability as reflected in PS-LTP priming appeared to be essential for the enhancement of learning in view of the observation that inhibition of PS-LTP priming was associated with impaired learning. Conversely, it was demonstrated that inhibition of CaMKII activity reduced contextual fear conditioning without affecting PS-LTP priming. This observation suggests that priming of PS-LTP and activation of CaMKII represent two essential mechanisms that may contribute independently to long-term memory.
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PMID:Priming of long-term potentiation in mouse hippocampus by corticotropin-releasing factor and acute stress: implications for hippocampus-dependent learning. 1197 54

Modulation of the sinus rate and contractile force by taurine at different extracellular Ca2+ concentrations ([Ca2+]o) was examined using rat right atria loaded with forced swimming stress. Serum concentration of corticosterone profoundly increased in stress-loaded rats as compared with native rats. The taurine level in serum also increased in stress-loaded rats, but was not changed in the different heart tissues and aorta. Heat-shock protein (HSP72) was detectable in cardiac muscles and in the lumen of cardiac blood vessels of stress-loaded rats using a monoclonal antibody. Increasing [Ca2+]o (from 0.9 to 3.6 mM) enhanced the sinus rate and contractile force in a [Ca2+]o-dependent fashion in native rats, but not in stress-loaded rats. Taurine (1-20 mM) caused a negative chronotropic and inotropic effect in a concentration-dependent manner. At 1.8 mM [Ca2+]o, the negative chronotropic effect of taurine (10-20 mM) was attenuated in stress-loaded rats as compared with native rats. These results indicate that swimming stress causes a release of taurine into the serum and reduces the sensitivity to [Ca2+]o. Taurine administration might, in part, exhibit the protective actions on acute stress-induced responses.
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PMID:Cardiac functions and taurine's actions at different extracellular calcium concentrations in forced swimming stress-loaded rats. 1211 26

Effect of ciliary neurotrophic factor (CNTF) on behavior and morphology of hippocampal neurons were observed and its mechanisms in rats were explored by Nissl staining, Bielschowsky-Gros-Lawrentjew staining, transmission electron microscopy, behavior determination, primary culture of hippocampal neuron, running photography of living cell, whole-cell patch clamp recording, detection of intracellular free Ca2+ and immunohistochemical detection of P53 protein. The results showed that there was no statistically significant change in the morphology of hippocampal neurons as a result of acute stress. The behavioral activity was increased during acute stress stage, which was not affected by CNTF. In chronic stress stage, neuronal damage in hippocampus was significant, and behavioral activity was significantly decreased under basal line. Administration of CNTF into bilateral hippocampus prevented neurons from damage and improved behavior. In vitro, CNTF could significantly suppress channel current, intracellular Ca2+ content and the expression of P53 protein in the nucleus induced by glutamate. The results suggested that the protective effect of CNTF may involve rapid effects on cell membrane and cytoplasma, and delayed effects on nucleus, thereby improve behavioral defects.
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PMID:[Protective effect of ciliary neurotrophic factor on the hippocampal neuronal damage induced by stress and its mechanisms in rats]. 1254 30

The creatine kinase (CK) system is involved in the rapid transport of high-energy phosphates from the mitochondria to the sites of maximal energy requirements such as myofibrils and sarcolemmal ion pumps. Hearts of mice with a combined knockout of cytosolic M-CK and mitochondrial CK (M/Mito-CK(-/-)) show unchanged basal left ventricular (LV) performance but reduced myocardial high-energy phosphate concentrations. Moreover, skeletal muscle from M/Mito-CK(-/-) mice demonstrates altered Ca2+ homeostasis. Our hypothesis was that in CK-deficient hearts, a cardiac phenotype can be unmasked during acute stress conditions and that susceptibility to ischemia-reperfusion injury is increased because of altered Ca2+ homeostasis. We simultaneously studied LV performance and myocardial Ca2+ metabolism in isolated, perfused hearts of M/Mito-CK(-/-) (n = 6) and wild-type (WT, n = 8) mice during baseline, 20 min of no-flow ischemia, and recovery. Whereas LV performance was not different during baseline conditions, LV contracture during ischemia developed significantly earlier (408 +/- 72 vs. 678 +/- 54 s) and to a greater extent (50 +/- 2 vs. 36 +/- 3 mmHg) in M/Mito-CK(-/-) mice. During reperfusion, recovery of diastolic function was impaired (LV end-diastolic pressure: 22 +/- 3 vs. 10 +/- 2 mmHg), whereas recovery of systolic performance was delayed, in M/Mito-CK(-/-) mice. In parallel, Ca2+ transients were similar during baseline conditions; however, M/Mito-CK(-/-) mice showed a greater increase in diastolic Ca2+ concentration ([Ca2+]) during ischemia (237 +/- 54% vs. 167 +/- 25% of basal [Ca2+]) compared with WT mice. In conclusion, CK-deficient hearts show an increased susceptibility of LV performance and Ca2+ homeostasis to ischemic injury, associated with a blunted postischemic recovery. This demonstrates a key function of an intact CK system for maintenance of Ca2+ homeostasis and LV mechanics under metabolic stress conditions.
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PMID:Creatine kinase-deficient hearts exhibit increased susceptibility to ischemia-reperfusion injury and impaired calcium homeostasis. 1510 71

The phosphorylation of calcium/calmodulin-dependent protein kinase (CaMK) II, induced by an increase in the intracellular Ca2+ concentration, is involved in the alteration of brain functions such as memory formation. In the present study, we examined the influence of various immobilization stress paradigms on the phosphorylation of CaMKII (phospho-CaMKII) and CaMKII levels in the rat hippocampus. Immunoblot and immunohistochemical analyses were performed to examine the levels of CaMKII and phospho-CaMKII. Real-time quantitative polymerase chain reaction (PCR) was performed to analyse the mRNA levels of N-methyl-D-aspartic acid (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subtypes. Acute (single) and repeated (4 d), but not chronic (14 d), stress exposure of 45 min or longer duration significantly increased phospho-CaMKII levels without affecting the levels of CaMKII. Pre-treatment with NBQX, a selective AMPA receptor antagonist, significantly prevented this stress-induced increase. In contrast, two NMDA receptor antagonists, LY235959 and MK-801, showed no inhibitory effect on phospho-CaMKII levels during acute stress. Neither acute nor chronic stress changed mRNA levels of NMDA and AMPA receptors. These results demonstrate that immobilization stress promotes the phosphorylation of CaMKII. The increase in the intracellular Ca2+ concentration by the activation of AMPA receptors may play a role in the stress-induced phospho-CaMKII in the rat hippocampus.
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PMID:Influence of immobilization stress on the levels of CaMKII and phospho-CaMKII in the rat hippocampus. 1512 74

In teleosts, the stress hormone cortisol and the calcium regulatory hormone stanniocalcin (STC) are both involved in the regulation of ion balance. Under stressful conditions, ion balance is easily disturbed as stressors via the stress signals they evoke disturb easily and primarily gill function. The gills are key in fish gas exchange and ion regulation. The present work evaluates the effect of the pivotal stress signal cortisol, the eventual output of the stress axis on STC secretion in freshwater rainbow trout (Oncorhynchus mykiss). Plasma cortisol levels were manipulated by intraperitoneal injections of porcine ACTH(1-39) or dexamethasone (Dex), and plasma cortisol, STC and mineral status were assessed. A perifusion assay of trout Stannius corpuscles was validated and used to study the direct effects of stress-related signals on STC release. In perifusion, cortisol, adrenocorticotropic hormone (ACTH), and dexamethasone did not affect STC release. ACTH injections increase plasma cortisol (corresponding to an acute stress) and STC concentrations, but did not affect mineral status. Dexamethasone injections resulted either in a classical hypocortisolinemia or, unexpectedly, in hypercortisolinemia. However, independently of the resulting cortisol status Dex induced a chronic stress effect, as indicated by decreased plasma Na, Cl, and Ca levels, and increased plasma STC concentrations. The increased STC secretion cannot be explained by the classical elevation of plasma calcium concentration. Thus, plasma parameters other than calcium could be involved and we propose that STC secretion might be stimulated also by a decrease of NaCl concentrations, implying a broader function than the classical hypocalcemic action of STC.
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PMID:The stress axis, stanniocalcin, and ion balance in rainbow trout. 1520 Oct 64

Under acute stress conditions in the rat, there is rapid and transient increase in circulating prolactin (PRL). This leads to an elevated expression of the long form of PRLR (PRLR-L) first in the hypothalamus and the choroid plexus. This increase in PRL is involved in the inhibition of stress-induced hypocalcemia and gastric erosion. In this study we used rat PRL and a PRLR morpholino-antisense oligonucleotide to elucidate the mechanism by which hypothalamic PRLR mediates the inhibition of restraint stress in water (RSW)-induced hypocalcemia and gastric erosion. We found that this effect is largely mediated by PRLRs in the paraventricular nucleus (PVN), medial preoptic nucleus, and ventromedial hypothalamus. We also show that when measured after 7 h of RSW, microinjection of the PRLR antisense oligonucleotide into these areas down-regulates RSW-enhanced expression of PRLR-L protein in the PVN and increases the plasma PRL level, but does not affect plasma levels of another hormone, GH. Furthermore, our experiments demonstrated that under nonstress conditions, knockdown of the PRLR in the PVN significantly lowers circulating Ca2+ levels, but does not affect gastric erosion. These results suggest that PRL acting on the PRLR-L in the PVN is one of the critical pathways for regulating circulating Ca2+ levels under both acute stress and nonstress conditions.
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PMID:Prolactin receptor knockdown in the rat paraventricular nucleus by a morpholino-antisense oligonucleotide causes hypocalcemia and stress gastric erosion. 1584 20

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