Decarboxylation Of Dopa Research Articles

An isolated, perfused rat brain preparation, its spontaneous and stimulated activity.

An isolated, perfused rat brain preparation, its spontaneous and stimulated activity.

Drug-induced changes in monoamine levels in the sympathetic adrenergic ganglion cells and terminals. A histochemical study.

AbstractNorberg, K.‐A. Drug‐induced changes in monoamine levels in the sympathetic adrenergic ganglion cells and terminals. A histochemical study. Acta physiol. scand. 1965. 65, 221–234.— The cell bodies of peripheral adrenergic neurons in rat sympathetic ganglia have been studied and compared with the adrenergic nerve terminals in respect of drug‐induced changes in CA levels and uptake‐accumulation of CA, DOPA and 5‐HTP, using the histochemical fluorescence method of Falck and Hillarp. The cell bodies show about the same rapid depletion as the terminals following the administration of reserpine and a‐MMT but recover much more quickly. After m‐tyrosine, depletion and recovery occur rapidly and simultaneously in both parts of the neuron. The findings are in accordance with the view that the transmitter granules are formed in the cell bodies. The increased NA content observed in the superior cervical ganglion following the administration of MAO inhibitors was found to be localized predominantly to the cell bodies of the adrenergic neuron. The cells react largely as two different populations: one showing a more or less pronounced amine increase, the other no or only a slight increase. — An accumulation of CA is found in the adrenergic neuron but not in other types of peripheral neurons following the administration of DA, NA or L‐DOPA. The efficient reserpine‐insensitive mechanism for the uptake‐concentration of NA that is localized to the level of the cell membrane of the adrenergic axons and terminals (Hamberger et al. 1964, Malmfors 1965) is present also in the cell bodies. — As regards the uptake or possibly decarboxylation of DOPA and 5‐HTP, the adrenergic neuron shows a marked specificity for DOPA. — The experiments show that the cell bodies and terminals have qualitatively the same properties.

Items from the Pharmacy Bulletin, Peter Bent Brigham Hospital

Methyldopate hydrochloride (Aldomet ester hydrochloride), also known as methyldopa (Aldomet, Merck Sharp & Dohme). This is an antihypertensive compound which acts as a decarboxylase inhibitor. It inhibits the metabolic decarboxylation of dopa, thereby interfering with the formation of dihydroxyphenethylamine (dopamine), a precursor of norepinephrine. It also inhibits the formation of serotonin from 5‐hydroxytryptophan (5‐HTP).

Influence of chlorpromazine on decarboxylases of aromatic amino acids

In vitro 10 −4 M chlorpromazine did not influence decarboxylation of 5-hydroxytryptophan (5HTP) and 3 : 4-dihydroxyphenylalanine (dopa) in supernatant of rat brain and kidney. 10 −3M chlorpromazine only inhibited dopa decarboxylation in brain supernatant to which no pyridoxal-5′-phosphat (py-5-p) had been added. Pretreatment of intact rats with high doses of chlorpromazine had no significant effect on decarboxylation of dopa or 5HTP in total homogenates or supernatant of brain. In supernatant of kidney of rats pretreated with chlorpromazine there was, however, a 30–70 per cent rise in decarboxylation of dopa and 5HTP, provided that no py-5-p was added to the incubation medium. The results are discussed with regard to the effects of chlorpromazine on the metabolism of py-5-p and aromatic monoamines.

Studies on 5-hydroxytryptophan decarboxylase. II. Additional inhibition studies and suggestions on the nature of the enzymic site

1. 1. The inhibition of 5-HTP decarboxylation by 3,4′-dihydroxy-3′-carboxychalcone, 3,4,4′-trihydroxy-3′-carboxychalcone and 1-(5-hydroxyindolyl-3)-2-(3-carboxy-4-hydroxybenzoyl)ethylene was found to be competitive at both pH 6.8 and pH 8.0. 2. 2. The K m for 5-HTP decarboxylation was estimated to be 4.0 × 10 −5 at pH 8.0 and 1.7 × 10 −4 at pH 6.8. 3. 3. Preincubation experiments appear to rule out the possibility that 5-HTP irreversibly combines at a DOPA site while reacting at a different site. It appears possible but unlikely that DOPA irreversibly binds at a 5-HTP site while reacting at a different site. 4. 4. These experiments would seem to strengthen the view that one enzymic site is involved in the decarboxylation of DOPA and 5-HTP.