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)

The centrally active muscarinic agonist, oxotremorine, elicited an up to 2-fold dose-dependent (0.25-1.5 mg/kg) increase in the activity of tyrosine hydroxylase (TH) in the rat nucleus locus coeruleus (LC) and adrenal medulla. The response occurred in LC after 24 to 48 hours and in adrenal medulla by 4 to 8 hours, peaked in LC at 72 hours and adrenal medulla at 16 to 24 hours and persisted up to 2 weeks in both tissues. In brain the effect appeared confined to cell bodies of noradrenergic neurons. The activity of dopamine beta-hydroxylase increased in adrenal medulla (40%) but not in brain. Immunotitration with anti-TH serum demonstrated that the increase of TH activity in LC is due to increased catalytic activity (activation), whereas in adrenal medulla it is due to a transynaptically mediated accumulation of enzyme protein (induction). Physostigmine (1.0 mg/kg), pilocarpine (25-50 mg/kg) and nicotine (10 mg/kg) increased TH activity in LC and adrenal. We conclude that stimulation of central cholinergic receptors of the muscarinic type results in a delayed and protracted activaiton of TH but not of dopamine beta-hydroxylase in cell bodies of central noradrenergic neurons, and reflexly, to transynaptic induction of TH and dopamine beta-hydroxylase in the adrenal medulla.
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PMID:Tyrosine hydroxylase: delayed activation in central noradrenergic neurons and induction in adrenal medulla elicited by stimulation of central cholinergic receptors. 1 97

Adult male Sprague-Dawley rats were given hourly injections of physostigmine for 1--4 h, and the effect of this treatment on dopamine (DA) and noradrenaline (NA) content or on DA and NA was estimated by measuring the decline in these amines produced following the inhibition of tyrosine hydroxylase with alpha-methyl-p-tyrosine (alpha MPT). In later experiments oxotremorine was administered instead of physostigmine at hourly intervals for 2 h. Physostigmine administration resulted in a highly significant increase in the depletion of NA produced by alpha MPT indicating that the turnover of NA was increased by this drug. This effect was observed in the medial basal hypothalamus and anterior hypothalamus but not in the telencephalon-thalamus. Oxotremorine also produced an increase in NA turnover, but this drug was effective in all three brain areas. Atropine pretreatment blocked the effect of both physostigmine and oxotremorine on NA turnover. However, in the case of physostigmine, atropine was only effective if it was given 30 min before each injection of physostigmine. Mecamylamine, a nicotine blocker, did not reverse the effect of physostigmine on NA turnover. These results suggest that there is a cholinergic input via muscarinic receptors which influences the activity of noradrenergic pathways terminating in the anterior or medial basal hypothalamus.
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PMID:Evidence for a cholinergic influence on catecholaminergic pathways terminating in the anterior and medial basal hypothalamus. 48 84

The rate of dopa synthesis in the rat superior cervical ganglion was increased 4- to 6-fold during continuous electrical stimulation of the cervical sympathetic trunk at 10 Hz for 30 min. This increase was only partially blocked by 3 mM hexamethonium and was not significantly affected by 6 microM atropine. In the presence of both hexamethonium and atropine, nerve stimulation still produced a 2- to 4-fold increase in dopa synthesis. Physostigmine increased dopa synthesis in both control and stimulated ganglia. This effect of physostigmine was completely blocked by hexamethonium and atropine. Dopa synthesis was also significantly increased when ganglia were incubated in a medium containing an elevated concentration of K+ (55 mM). This stimulatory effect of high K+ was totally dependent on the presence of Ca2+ in the medium, was decreased by 60% by prior decentralization of the ganglion, and was unaffected by hexamethonium and atropine. The data demonstrate that tyrosine hydroxylase activity is rapidly increased after preganglionic nerve stimulation and suggest that this increase is mediated in part by acetylcholine and in part by a second (noncholinergic) transmitter. The effects of an elevated K+ concentration may be mediated both by the release of a noncholinergic transmitter from the preganglionic nerve terminals and by direct depolarization of the ganglionic neurons.
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PMID:Acute transsynaptic regulation of tyrosine 3-monooxygenase activity in the rat superior cervical ganglion: evidence for both cholinergic and noncholinergic mechanisms. 613 84