Article (Scientific journals)
Regional Distribution and Control of Tyrosine Hydroxylase Activity in the Quail Brain
Baillien, M.; Foidart, Agnès; Balthazart, Jacques
1999In Brain Research Bulletin, 48 (1), p. 3-17
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Abstract :
[en] Tyrosine hydroxylase (TH) activity, the rate-limiting step in the synthesis of catecholamines, was quantified in the preoptic area-hypothalamus of adult male Japanese quail by a new assay measuring the tritiated water production from 3,5-[3H]-L-tyrosine. Maximal levels of activity were observed at a 20-25 microM concentration of substrate, with more than 50% inhibition of the activity being recorded at a 100 microM concentration. TH activity was linear as a function of the incubation time during the first 20 min and maximal at a pH of 6.0. TH was heterogeneously distributed in the quail brain with highest levels of activity being found (in decreasing order) in the mesencephalon, diencephalon, and telencephalon. Given the large size of the telencephalon, this is the brain area that contains, as a whole, the highest level of enzyme activity. TH inhibitors that have been well-characterized in mammals, such as 3-iodo-L-tyrosine and L-alpha-methyl-p-tyrosine (AMPT) completely inhibited the enzyme activity at a 100 microM concentration. In mammals, the accumulation of catecholamines exerts a negative feedback control on TH activity. Similar controls were observed in the quail brain. Two inhibitors of the DOPA decarboxylase that should lead to accumulation of DOPA depressed TH activity by 60% or more, and the inhibitor of the dopamine beta-hydroxylase, fusaric acid that should cause an accumulation of dopamine, suppressed 90% of the TH activity. The addition of exogenous DOPA, dopamine, or norepinephrine to the brain homogenates also strongly inhibited TH activity, independently confirming the feedback effects of the enzyme products on the enzyme activity. These data demonstrate that TH activity in the quail brain is heterogeneously distributed and acutely regulated, as it is in mammals, by the accumulation of its products and of the derived catecholamines.
Disciplines :
Neurosciences & behavior
Zoology
Author, co-author :
Baillien, M.
Foidart, Agnès ;  Université de Liège - ULiège > Services généraux (Faculté de médecine) > Service administratif de la Faculté (Médecine)
Balthazart, Jacques  ;  Université de Liège - ULiège > Département des sciences biomédicales et précliniques > Biologie de la différenciation sexuelle du cerveau
Language :
English
Title :
Regional Distribution and Control of Tyrosine Hydroxylase Activity in the Quail Brain
Publication date :
01 January 1999
Journal title :
Brain Research Bulletin
ISSN :
0361-9230
eISSN :
1873-2747
Publisher :
Elsevier, Netherlands
Volume :
48
Issue :
1
Pages :
3-17
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 27 April 2009

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