UMLS:C0009443 - FACTA Search

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Query: UMLS:C0009443 (cold)
92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The trans-synaptic induction of tyrosine hydroxylase [tyrosine 3-monooxygenase; EC 1.14.16.2, L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating)] in adrenal medulla and sympathetic ganglia by short-term (1-2 hr) cold stress (4 degrees) exhibits a circadian rhythm which seems to be causally related to the diurnal changes in adrenal glucocorticoid synthesis. In induction is maximal during the morning hours, when plasma corticoid concentrations (reflecting corticoid synthesis in the adrenal cortex) are minimal. In contrast, initiation of tyrosine hydroxylase induction in sympathetic ganglia is only possible in the afternoon. These observations suggest that tyrosine hydroxylase inducibility in the adrenal medulla is optimal during periods of low corticoid synthesis (the adrenal medulla is exposed to excessively high corticoid concentrations directly originating from the adjacent cortex), whereas in sympathetic ganglia an induction is only possible during the period of high plasma corticoid concentrations. This assumption is supported by the observation that in the first postnatal weeks, when the pituitary--adrenocortical system is not yet operating and plasma corticoid concentrations are low, initiation of tyrosine hydroxylase induction in the adrenal medulla is possible at any time of the day, whereas in sympathetic ganglia it is not possible at all. However, after administration of glycocorticoids initiation of tyrosine hydroxylase induction by short-term cold stress is also possible in newborn animals and in adults during the morning hours. The importance of glucocorticoids as modulators for the initiation of trans-synaptic tyrosine hydroxylase induction can also be deduced from the observation that in sympathetic ganglia kept in organ cultures and induction of the hydroxylase by cholinomimetics is only possible when glycocorticoids are added to the culture medium.
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PMID:Circadian rhythm of tyrosine hydroxylase induction by short-term cold stress: modulatory action of glucocorticoids in newborn and adult rats. 23 60

A subcutaneous injection of an oil suspension of l-epinephrine (270 mumol/kg), dopamine (270 mumol/kg) or l-norepinephrine (270 mumol/kg), when administered with phenoxybenzamine (32 mumol/kg i.p.) to blocl alpha adrenergic effects, increases the cyclic 3', 5'-adenosine monophosphate (cAMP) content in superior cervical ganglia (SCG) of rats. The increase is highest after l-epinephrine and dopamine and is barely detectable after l-norepinephrine; it lasts longer than 2 hours after l-epinephrine, about 30 minutes after dopamine and is fleeting after l-norepinephrine. The duration of the increase in cAMP elicited by l-epinephrine in SCG of rats is dose-related. Furthermore, when the cAMP increase lasts longer than 90 minutes, 48 hours later the tyrosine hydroxylase (TH) activity in SCG is increased. l0Epinephrine (150 mol/kg s.c.) induces TH in decentralized ganglia. One injection of l-isoproterenol (77 mol/kg i.p.) increases cAMP concentrations in intact and decentralized SCG. This increase lasts only 30 minutes and fails to induce TH 48 hours later. However, if the increase of cAMP concentration is prolonged by four successive injections of l-isoproterenol (15 30-minute intervals) the TH activity of intact and decentralized SCG is increased 48 hours later.l-Isoproterenol (four injections of 77 mumol/kg, each) and l-epinephrine (270 mumol/kg) fail to induce TH in the adrenal medulla. dl-Propranolol (125 mumol/kg i.p.) injected 30 minutes before l-isoproterenol blocks the increase of cAMP content and the delayed induction of TH activity in SCG. The elevation of TH activity elicited in SCG by beta adrenergic receptor agonists is always preceded by an increase of cAMP concentration lasting 90 minutes or longer. However, the induction of TH elicited by cold exposure or by reserpine administration can occur without an apparent increase in ganglionic cAMP concentration.
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PMID:Induction of tyrosine hydroxylase elicited by beta adrenergic receptor agonists in normal and decentralized sympathetic ganglia: role of cyclic 3',5' - adenosine monophosphate. 23 17

To investigate the role played by hypothalamic noradrenaline (NE) in the regulation of TRH-TSH release during tonic and cold activated conditions, drugs and surgical procedures able to interfere with central NE tonus were utilized. The time course of the effect of alpha-methyl-para-tyrosine (alpha-MpT) on basal TSH secretion was followed. The tyrosine hydroxylase (TH) inhibitor was unable to modify TSH plasma levels, whereas NE hypothalamic content decreased beginning with the third hour. The acute release of TSH evoked by cold exposure (CE) was prevented by pretreatment with alpha-MpT 1 h before; when alpha-MpT was followed 40 min later by clonidine, a central noradrenergic stimulating agent, TSH response to cold, previously blocked by the TH inhibitor was restored. Intraventricular injection of 10 micrograms of clonidine hydrochloride in unstimulated rats caused a significant rise of basal TSH levels 3, but not 10 min after the administration. Complex deafferentation of the medial basal hypothalamus (MBH), which destroys all the NE fibers afferent to this area, caused no change of thyrotropin secretion in basal conditions. Deafferented animals did not show any acute increase of TSH in response to CE. The results of this study provide evidence that NE may be the catecholamine (CA) mediating the rise in TSH following CE and that the direct stimulation of central NE receptors can evoke a massive TSH release from the anterior pituitary gland also in basal conditions.
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PMID:The role of central noradrenergic neurons in the control of thyrotropin secretion in the rat. 40 Oct 25

The synthesis of catecholamines (CA) has been studied in the heart, spleen, submaxillary glands and adrenals of rats exposed to 4 degrees C for 2.5, 24 or 48 h. The synthesis rate has been estimated 30 min after an i.v. injection of 3H tyrosine (TY) by the evaluation of the ratio: 3H-CA specific activity/3H-TY specific activity. In the sub-maxillary glands, cold exposure reduced the noradrenaline (NA) synthesis by 40% at times 24 and 48 h. In the spleen, NA synthesis was multiplied by a factor 1.6 at times 2.5 and 24 h and 2.8 at time 48 h. In the heart, it was increased by a factor 1.3 after 2.5 h, 2.8 after 24 h and 5.5 after 48 h: an important fall in cardiac NA level was observed during the first 24 h of cold exposure indicating that the synthesis capability was unsufficient to compensate the cold-induced NA release. In the adrenals, adrenaline + NA synthesis was not significantly enhanced during the first 24 h of cold exposure and increased by a factor 2.4 at time 48 h. The important increases in CA synthesis which are observed during the 24-48 h interval are likely consecutive to the induction of tyrosine hydroxylase which has been reported in the rat exposed to cold.
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PMID:Evolution in vivo of the synthesis rate of catecholamines in various peripheral organs of the rat during cold exposure. 103 28

We have used microdialysis to measure the in vivo level of tyrosine hydroxylation in hippocampus of the freely moving rat. An inhibitor of aromatic amino acid decarboxylase, NSD-1015, was administered through the dialysis probe and the resulting accumulation of 3,4-dihydroxyphenylalanine (DOPA) in extracellular fluid of hippocampus was quantified. Administration of the tyrosine hydroxylase inhibitor, alpha-methyl-p-tyrosine, decreased extracellular DOPA to undetectable level. In addition, both systemic and local application of clonidine, an alpha 2-adrenergic agonist, produced a decrease in extracellular DOPA. In response to acute tail shock, a significant increase in extracellular DOPA was observed. Thus, it appears that in vivo accumulation of DOPA after local administration of NSD-1015 provides a reliable index of hippocampal tyrosine hydroxylation. We have used this technique to investigate whether prior exposure to chronic stress alters the in vivo level of tyrosine hydroxylation in hippocampus under basal conditions as well as in response to a novel stressor. In rats previously exposed to chronic cold stress, the basal accumulation of extracellular DOPA did not differ from naive controls. Acute tail shock, however, produced a significantly greater and more prolonged elevation in extracellular DOPA of chronically stressed rats. These data suggest that enhanced biosynthetic capacity of noradrenergic terminals may be one mechanism underlying adaptation to chronic stress.
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PMID:Enhanced tyrosine hydroxylation in hippocampus of chronically stressed rats upon exposure to a novel stressor. 134 67

Recent studies have demonstrated that chronic stress increases the firing rate and expression of tyrosine hydroxylase (TH) in neurons of the locus coeruleus (LC), the major noradrenergic nucleus in brain. The present study was undertaken to examine the influence of chronic stress and other treatments known to influence the activity of LC neurons on the cyclic AMP (cAMP) second messenger system in these neurons. Chronic (5 days) cold exposure significantly increased levels of TH immunoreactivity in the LC, as previously reported, but not in substantia nigra (SN) or ventral tegmentum (VT), two dopaminergic nuclei studied for comparison. Chronic cold exposure increased levels of cAMP-dependent protein kinase activity in soluble, but not particulate, fractions of the LC, and increased basal and GTP- and forskolin-stimulated adenylate cyclase activity in this brain region. In contrast, levels of the protein kinase and adenylate cyclase in VT, SN, and frontal cortex were not significantly influenced by cold exposure. To study further the relationship between regulation of LC firing rate, TH expression, and the cAMP system in the LC, other treatments known to influence TH were examined. Reserpine treatment, shown previously to increase levels of TH, was found to increase both LC firing rate and levels of soluble cAMP-dependent protein kinase activity in the LC. 6-Hydroxydopamine, shown previously to increase levels of TH and firing rate of LC neurons, also increased soluble levels of protein kinase activity. Other treatments known to either increase (adrenalectomy) or decrease (chronic imipramine) levels of TH in the LC were also found to increase or decrease, respectively, levels of cAMP-dependent protein kinase activity in this brain region.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Coordinate regulation of the cyclic AMP system with firing rate and expression of tyrosine hydroxylase in the rat locus coeruleus: effects of chronic stress and drug treatments. 134 39

When male rats were injected four times (once every 2 hr) with 5 mg/kg methamphetamine (METH) at an environmental temperature of 23 degrees C, transient changes occurred in the levels of striatal dopamine (DA) and the regulation of striatal DA release. Striatal DA levels were minimally affected 1 day after METH treatment, but 3 days after METH treatment, striatal DA levels decreased to approximately 40% of control. DA levels returned to 70% of control 2 weeks after METH. Similarly, striatal tyrosine hydroxylase (TH) activity decreased to approximately 50% of control activity 3 days after METH treatment at 23 degrees C, but did not differ from controls at 1 or 14 days after METH treatment. No changes in striatal DA levels were observed in rats treated with four doses of 5 mg/kg METH at an environmental temperature of 4 degrees C. Striatal DA levels decreased modestly to approximately 70% of controls 3 days after treatment with four doses of 10 mg/kg METH at 4 degrees C, but DA levels returned to control levels 14 days after METH treatment. Furthermore, striatal TH activity was not affected by 10 mg/kg METH at 4 degrees C. Thus, a cold environmental temperature (4 degrees C) reduced the effects of METH on striatal DA levels and striatal TH activity. Changes in the presynaptic regulation of DA release after either 5 mg/kg (23 degrees C) or 10 mg/kg (4 degrees C) METH treatment were determined in vitro using striatal slices.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The influence of environmental temperature on the transient effects of methamphetamine on dopamine levels and dopamine release in rat striatum. 134 46

Previous studies have demonstrated that chronic stress increases and antidepressant treatments decrease levels of tyrosine hydroxylase (TH) in locus coeruleus (LC). In the present study, the influence of chronic antidepressant treatment on the induction of TH immunoreactivity in response to cold stress is examined. It was found that chronic imipramine pretreatment (18 days) attenuated the induction of TH in response to cold stress, resulting in levels of TH immunoreactivity not different from control. In contrast, imipramine pretreatment for 1 or 7 days was not sufficient to normalize the stress-induced elevation of TH immunoreactivity. These findings raise the possibility that the therapeutic action of antidepressants may be derived, in part, from the ability of these treatments to normalize levels of TH and thereby the function of the NE neurotransmitter system under conditions of stress.
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PMID:Chronic imipramine treatment normalizes levels of tyrosine hydroxylase in the locus coeruleus of chronically stressed rats. 135 7

It is well documented that cold stress induces a rapid trans-synaptically mediated increase in the relative abundance of rat adrenomedullary tyrosine hydroxylase (TH) mRNA. To investigate the transcriptional mechanisms regulating the cold stress response, we have employed a gel mobility shift assay, using DNA fragments prepared from the proximal 5' flanking region of the bovine TH gene as a heterologous molecular probe. In pilot studies, this region of the bovine TH promoter (nucleotides -246 to +21) was fused to the bacterial reporter gene, chloramphenicol acetyltransferase, and the chimeric construct transfected into human neuroblastoma SK-N-BE(2)-C, hepatoma HepG2, and rat pheochromocytoma PC-12 cells. Results of this analysis indicate that the proximal 5' flanking region of the bovine TH gene contains sufficient information to drive transient reporter gene expression in both human and rat catecholaminergic clonal cell lines. The findings derived from the gel mobility shift studies demonstrate that cold exposure causes rapid and selective alterations in the binding of adrenomedullary nuclear proteins to the proximal 5' flanking region of the TH gene. The most striking cold stress-induced alteration in DNA/nucleoprotein binding occurs in a region of the TH promoter (nucleotides -246 to -189) which contains an element bearing marked sequence similarity to an AP1 binding site and is highly conserved among animal species. This alteration occurs within 1 hr of cold exposure and persists for up to 48 hr after the onset of stress. The results of adrenal denervation experiments indicate that the cold-induced change in DNA/nucleoprotein binding is neurally mediated, requiring intact sympathetic innervation of the gland.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cold-induced alterations in the binding of adrenomedullary nuclear proteins to the promoter region of the tyrosine hydroxylase gene. 136 May 41

The release and synthesis of norepinephrine (NE) in hippocampus were measured in naive and chronically cold-stressed rats in response to acute tail-shock stress. Using in vivo microdialysis, it was determined that the basal extracellular concentrations of NE and 3,4-dihydroxyphenylacetic acid (DOPAC) in hippocampus were the same in the two groups. However, 30 min of intermittent tail shock produced a greater elevation of extracellular NE and 3,4-dihydroxyphenylacetic acid in the chronically cold-stressed rats than in the native controls. In hippocampus, the extracellular concentration of DOPAC may reflect NE biosynthesis, and thus the enhanced DOPAC response in the chronically stressed rats suggests an increase in NE synthesis. In order to investigate this possibility, two further methods of assessing NE biosynthesis were employed. Tyrosine hydroxylase (TH) activity was assayed in vitro in the presence of saturating concentrations of cofactor. No change in maximal TH activity could be detected in hippocampus of chronically cold-stressed rats. In addition, the in vivo rate of tyrosine hydroxylation in cold-stressed rats was measured by the accumulation of 3,4-dihydroxyphenylalanine in tissue following inhibition of aromatic amino acid decarboxylase. It was found that, whereas basal synthesis was the same in both groups of rats, synthesis accompanying a novel stressor was increased to a greater extent in the chronically stressed rats.
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PMID:Prior exposure to chronic stress results in enhanced synthesis and release of hippocampal norepinephrine in response to a novel stressor. 167 4

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