Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In previous reports, methamphetamine was shown to depress tyrosine hydroxylase (TH) activity in the rat corpus striatum. To evaluate further the mechanism of this decrease in TH activity, enzyme activity was measured in the rat corpus striatum and substantia nigra after repetitive and single-dose methamphetamine administration. Following repeated doses of methamphetamine, nigral TH activity decreased and reached 45% of controls at 12 hr and returned to normal at 60 hr. Striatal TH activity decreased to 40% of control at 36 hr and returned toward normal at 60 hr. When methamphetamine was administered every 6 hr for 30 hr and then discontinued, nigral TH activity returned toward control levels 4 days prior to recovery of striatal TH activity. Methamphetamine initially increased striatal dopamine levels at 6 hr (170% of control). Dopamine levels then decreased in parallel with striatal TH activity but failed to increase as the enzyme recovered. Concurrent administration of chlorpromazine with methamphetamine prevented the methamphetamine-induced decrease in nigral and striatal TH activity and striatal dopamine levels. The results indicate that the methamphetamine-induced depression of striatal and nigral TH activity may be related to increased stimulation of dopamine receptors in the striatum.
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PMID:Influence of methamphetamine on nigral and striatal tyrosine hydroxylase activity and on striatal dopamine levels. 0 86

Repeated exposure of rats to thyrotropin releasing hormone produced a dose- and time-dependent increase in spontaneous locomotor activity accompanied by an increase in brain stem tyrosine hydroxylase. Dopamine levels in cerebral cortex were increased maximally by 34% in animals receiving thyrotropin releasing hormone at a dosage of 2 mg/kg for 10 days. The concentrations of brain stem tyrosine and cerebral cortex norepinephrine remained unaltered in response to thyrotropin releasing hormone treatment. Our data suggest that administration of thyrotropin releasing hormone increases the synthesis and perhaps the turnover of brain catecholamines and that this may constitute an underlying mechanism for the anti-depressant action of this synthetic hormone.
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PMID:Changes in brain catecholamines and spontaneous locomotor activity in response to thyrotropin releasing hormone. 1 49

Dopamine-beta-hydroxylase (DBH) activity in serum, DBH and tyrosine hydroxylase (TH) activities in mesenteric vessels, and DBH and TH activities in locus coeruleus and hypothalamus of brain did not differ significantly between spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKR) at 16 weeks of age when hypertension of SHR was fixed. In contrast, DBH and TH activities in vas deferens and adrenal glands were significantly higher in SHR than in WKR. These changes in SHR at 16 weeks of age after establishment of hypertension are directly opposite those reported previously in SHR at 3 weeks of age before the onset of hypertension.
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PMID:Norepinephrine-synthesizing enzymes in brain, adrenals and peripheral sympathetic nerves of spontaneously hypertensive rats. 2 83

The selective destruction of neuronal perikarya via intracerebral injections of kainic acid was used to elucidate the cellular location of four neurotransmitter-related enzymes in the substantia nigra (SN). Two weeks after intranigral injections of kainic acid, dopamine-sensitive adenylate cyclase, glutamic acid decarboxylase (GAD), choline acetyltransferase (CAT) and acetylcholinesterase (AChE) were measured in the SN. Histological examination of the SN, and a reduction of striatal tyrosine hydroxylase (TH) activity by 94%, confirmed the extensive loss of neuronal cell bodies in the SN. Dopamine stimulation of adenylate cyclase was not reduced in the lesioned SN, supporting the view that dendritically-released dopamine can regulate cyclic AMP synthesis in afferent terminals to these dendrites. Nigral GAD activity was significantly reduced by the lesions, suggesting that there are GAD-containing perikarya in the SN. CAT activity was not affected by the kainic injections, indicating the absence of cholinergic perikarya in the SN. Nigral AChE activity was significantly decreased after kainic injections, thus confirming the presence of AChE within the nigral perikarya. The results suggest that dopamine-sensitive adenylate cyclase and CAT are located within afferents to the SN, while GAD and AChE are found, to some extent at least, in neuronal soma of the SN. The differentail effects of kainic acid on these enzymes suggest that this compound may be a useful neurochemical tool with which to determine the cellular distribution of enzyme systems in the central nervous system.
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PMID:The use of kainic acid in the localization of enzymes in the substantia nigra. 2 84

The PAP unlabelled antibody enzyme method of Sternberger was used for the histochemical demonstration of LHRH and the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH) in the hypothalamus of the adult male and pregnant female rat. The sections for light and electron microscopy were serially treated with normal goat serum, LHRH antiserum and/or TH antiserum, goat anti-rabbit IgG, PAP complex and 3,3'-diaminobenzidine (DAB) or 4-Cl-1-naphtol. LHRH-positive cell bodies were discernible in the medial preoptic area. The LHRH-positive terminals were densely localized in the organum vasculosum of the lamina terminalis and in the perivascular region of the median eminence (PVME). Dopamine (DA)-positive cell groups (TH-positive perikarya) were discernible in the arcuate nucleus, and its terminals were densely localized in the PVME. The simultaneous identification of LHRH and DA in the distinctive neuronal system of the median eminence was possible with the PAP double staining technique, in which LHRH is revealed as a brown precipitate with DAB, and TH is revealed as a blue reaction product with naphtol. The LHRH neuronal system did not contain TH and vice versa. The ultrastructural study revealed that LHRH was localized in large vesicles with a diameter of 100 nm within the axon terminals, while TH was localized in the endoplasmic reticulum, the neurotubules and small vesicles with a diameter of 50 nm within the DA neuron. The axo-axonic contact of LHRH and DA terminals was demonstrated in close proximity to portal vessels, suggesting the synaptic influence of DA on the release of LHRH into these vessels.
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PMID:Simultaneous localization of LHRH and catecholamines in rat hypothalamus. 3 6

Dopamine and its metabolites homovanillic acid and dihydroxyphenylacetic acid, noradrenaline, serotonin and its metabolite 5-hydroxyindoleacetic acid, and tryptophan and its metabolite kynurenine have been assayed in 9 schizophrenic and 10 control brains, together with the monoamine-related enzymes tyrosine hydroxylase monoamine oxidase, dopamine-beta-hydroxylase, and catechol-o-methyl-transferase. In schizophrenic brains dopamine, noradrenaline and serotonin were significantly increased in some areas of corpus striatum, but there were no significant changes in enzyme activity or monoamine metabolite concentrations in any of the brain areas examined. The findings are not consistent with theories that serotonin or noradrenaline stores are grossly depleted or noradrenaline neurones have degenerated, or that monoamine oxidase activity is abnormal, in schizophrenia, and provide no direct support for the hypothesis that dopamine neurones are overactive.
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PMID:Monoamine mechanisms in chronic schizophrenia: post-mortem neurochemical findings. 4 9

Postmortem changes in the activities of tyrosine hydroxylase, dopa decarboxylase, and dopamine-beta-hydroxylase were examined in various areas of rat brain. Tyrosine hydroxylase activity decreased in an exponential fashion with a half-time of two to four hours in caudate-putamen, substantia nigra, and locus ceruleus. Dopa decarboxylase activity remained within 20% of control values at five hours in these areas, but then decreased precipitously. Dopamine-beta-hydroxylase activity remained within 20% of control for at least 20 hours after death.
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PMID:Postmortem changes in brain catecholamine enzymes. 23 34

Catecholamine biosynthesis in tumor cells was studied in four patients, who expired from disseminated neuroblastoma. 1. The activity of tyrosine hydroxylase was detected in tumor tissues of all but one patient. 2. Dopamine-beta-hydroxylase activity was assayabel in almost all tissues, except in the primary tumor of one patient. 3. The enzyme activities in the metastatic lesions were at the same levels in two cases, but much higher in the other two cases, as those in the primary tumours. 4. It was learned that the urinary excretion of vanilmandelic acid (VMA) and homovanillic acid (HVA) in these patients reflects the tissue levels of catecholamine synthesizing enzymes as well as the tumor mass.
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PMID:Biochemical activity in the metastatic lesions of neuroblastoma. 24 12

The naturally occurring catecholamines, noradrenaline, adrenaline and dopamine, have been found in a wide range of animal and vegetable tissues, but are particularly associated with nervous tissue in animals. Of the many processes affecting the response to stimulation of catecholamine containing nerves, the synthesis of catecholamines, particularly the first enzymatic stage involving tyrosine hydroxylase, and the re-uptake process, whereby the nerve recovers much of the released catecholamine, appear to be the most significant. In peripheral tissues noradrenaline appears to be involved predominantly in the sympathetic control of blood pressure and flow while adrenaline is more important to metabolic processes especially fat and glucose turnover. Both may be released in increased amounts by various stimuli that cause stress or arousal in the body. Dopamine has not yet been shown to have any significant physiological function in peripheral tissues. In the central nervous system, noradrenaline and dopamine are the two main catecholamines. The working of the brain is complex and involves balanced interactions between a variety of neurotransmitters, known or as yet unrecognised. However, noradrenaline appears to play a role in the central control of blood pressure, and in determining mood and activity probably by affecting the emotional drives. Dopamine is certainly important in the control of motor pathways, as shown by the dopamine deficiency syndrome in Parkinson's disease, and is possibly of significance in the abnormal behaviour of psychotics. The role of the small concentration of adrenaline in the brain has yet to be fully established.
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PMID:Catecholamines: role in health and disease. 36

Levels of norepinephrine (NE) in the spinal cord tissue of nontraumatized cats are highest in the cervical and lumbar enlargements. A rather uniform but slightly increasing concentration gradient from cephalad to caudad is observed in the thoracic segments. A 500 gm-cm trauma at the T-5 or C-7 spinal cord segment did not demonstrate any significant increase in NE levels measured sequentially over a 4-hour period after trauma. Dopamine levels could not be detected in the nontraumatized or traumatized cat spinal cords. Four traumatized cats treated with alpha methyl tyrosine, a tyrosine hydroxylase inhibitor, and followed clinically for 5 months showed no improvement in neurological function when compared to untreated traumatized cats. This study does not support the norepinephrine hypothesis of experimental spinal cord trauma.
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PMID:Norepinephrine levels in experimental spinal cord trauma. Part 1: Biochemical study of hemorrhagic necrosis. 83 58


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