M F Mineyeva | PubMed Health

PubMed1978

Brain tyrosine hydroxylase: kinetic properties and regulation of the activity.

Electrical stimulation of rat hypothalamic synaptosome suspensions produced activation of tyrosine hydroxylase due to increase of the affinity for tyrosine and 6,7-dimethyl-5,6,7,8-tetrahydropterine cofactor, decrease of the affinity for dopamine and enhancement of substrate inhibition. Cocaine (10(-7) - 10(-5) M) in vitro caused enzyme activation; when administered to animals systemically (0.5 mg/kg) the drug produced inhibition of hypothalamic tyrosine hydroxylase probably through a receptor-mediated feedback mechanism.

Animals↗

PubMed1978

The effect of neuroleptics on brain tyrosine hydroxylase.

The effect of a number of neuroleptics and tricyclic antidepressants on the activity of rat hypothalamic tyrosine hydroxylase was studied utilizing a direct spectrophotometric method. All the neuroleptics (but not the antidepressants) were able to reverse the substrate inhibition of the enzyme occurring when the tyrosine concentration in the medium was increased. Haloperidol, haloanisone and fluphenazine were found to activate the enzyme at optimal tyrosine concentrations in contrast to other neuroleptics which reduced the enzyme activity. The systemic administration of fluphenazine and clozapine was followed by an increase in the activity of striatal and hypothalamic tyrosine hydroxylase. The same drugs failed to produce this effect when administered chronically for 8 days.

Amitriptyline↗