Studies on Tyrosine Hydroxylase System in Rat Brain Slices Using High-Performance Liquid Chromatography with Electrochemical Detection

Hirata, Yoko; Togari, Akifumi; Nagatsu, Toshiharu

doi:10.1111/j.1471-4159.1983.tb08130.x

Cited by 49 publications

(11 citation statements)

References 19 publications

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“…These findings support the validity of the DOPA assay for measuring tyrosine hydroxylase activity in synaptosomes. Similar conclusions regarding the validity of using the DOPA assay for monitoring tyrosine hydroxylase activity have been presented for in vivo brain measurements (Carlsson et al, 1972) and for in vitro assays of adrenal pheochromocytoma cells (Erny et al, 1981), superior cervical ganglion preparations (Ip et al, 1982), and, more recently, brain slices (Hirata et al, 1983).…”

Section: Egta (Mm)supporting

confidence: 54%

Dihydroxyphenylalanine Production in Rat Brain Striatal Synaptosomes: Stimulation by a Calcium Chelator

Haycock

Patrick

1984

Journal of Neurochemistry

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By inhibiting aromatic L-amino-acid decarboxylase (EC 4.1.1.28) in rat brain striatal synaptosomes, we have been able to measure dihydroxyphenylalanine production via high performance liquid chromatography-electrochemical oxidation. This dihydroxyphenylalanine assay was compared to a standard radioisotopic assay of catecholamine synthesis (14CO2 production from L-[1-14C]tyrosine) in terms of (1) units of activity, (2) effects of known inhibitory and stimulatory agents, and (3) effects of the calcium chelator, EGTA. The units of activity in the dihydroxyphenylalanine assay were 40% greater than the units in the radioisotopic assay, indicating a mixing of labeled and endogenous tyrosine pools before conversion of the labeled tyrosine to labeled dihydroxyphenylalanine. The inhibition of synthesis produced by either 3-iodotyrosine or 3,4-dihydroxyphenylethylamine was similar in the two assays, as was the stimulation produced by 8-bromo cyclic AMP. The calcium chelator, EGTA, also activated synthesis to the same extent in the two assays, indicating that the increase observed in the radioisotopic assay is not an artifact of altered precursor specific activity. These data thus indicate the general utility of the synaptosomal dihydroxyphenylalanine synthesis assay, and also demonstrate the specific advantages of this assay for analyzing the effects of agents such as EGTA, which can alter tissue catecholamine precursor levels.

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Section: Egta (Mm)supporting

confidence: 54%

Dihydroxyphenylalanine Production in Rat Brain Striatal Synaptosomes: Stimulation by a Calcium Chelator

Haycock

Patrick

1984

Journal of Neurochemistry

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“…The prevention of the conversion of L-DOPA to dopamine by NSD-1055 and NSD-1055-induced decrease in the tissue content of dopamine, as a result of decrease in newly synthesized dopamine, show that adequate concentrations of the drug were used. (Hirata et al, 1983).…”

Section: Resultsmentioning

confidence: 99%

“…However, in the present experiments we found that the same lower concentration of L-DOPA as that of dopamine inversely facilitated the release of noradrenaline. Hence, we further investigated whether or not L-DOPA produces biphasic actions via presynaptic regulatory mechanisms on the release of noradrenaline and dopamine in the absence and presence of pbromobenzyloxyamine (NSD-1055), a DOPA-decarboxylase inhibitor (Hirata et al, 1983). Part of this work was presented at the Ninth Annual Meeting of Japan Neuroscience Society (Goshima et al, 1985b).…”

Section: Introductionmentioning

confidence: 99%

Biphasic actions of L‐DOPA on the release of endogenous noradrenaline and dopamine from rat hypothalamic slices

Goshima

Kubo

Misu

1986

British J Pharmacology

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Effects of L‐DOPA on the release of endogenous noradrenaline and dopamine from rat hypothalamic slices evoked by electrical field stimulation at 5 Hz were investigated in the absence and presence of p‐bromobenzyloxyamine (NSD‐1055), a DOPA‐decarboxylase inhibitor. In the absence of NSD‐1055, L‐DOPA produced a facilitation of impulse‐evoked release of noradrenaline at 0.1 μM but not at 1 and 10 μM, and had no effect on the spontaneous release. On the other hand, L‐DOPA 0.1 to 10 μM dose‐dependently increased the spontaneous release of dopamine and the highest concentration only increased the evoked release and tissue content of dopamine. In the presence of NSD‐1055 10 μM, the increase in the spontaneous release of dopamine was prevented and L‐DOPA produced biphasic regulatory effects on the evoked release of noradrenaline and dopamine, a facilitation at 0.1 μM and an inhibition at 1 μM. The facilitation was antagonized by (‐)‐propranolol 0.1 μM, but not by the (+)‐isomer, whereas the inhibition was antagonized by S‐sulpiride 1 nM, but not by the R‐isomer. In conclusion, L‐DOPA appears to produce biphasic actions on the release of endogenous noradrenaline and dopamine from rat hypothalamic slices, not through its conversion to dopamine but through presynaptic regulatory mechanisms, an inhibition via dopamine receptors at a micromolar concentration and a facilitation via β‐adrenoceptors at the lower concentration.

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“…, 1963). The activities of phenylalanine hydroxylase (Milstien and Kaufman, 1975) and tyrosine hydroxylase (Hirata et al, 1983) were shown to increase with addition of 6-methyltetrahydropterin to the rat livtr slice system and BPH4 to the rat striatal slice system, respectively. These results suggest that phenylalanine and tyrosine hydroxylases are subsaturating for a cofactor in vivo.…”

Section: Discussionmentioning

confidence: 99%

(6R)‐Tetrahydrobiopterin Increases the Activity of Tryptophan Hydroxylase in Rat Raphe Slices

Sawada

Sugimoto

Matsuura

et al. 1986

Journal of Neurochemistry

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The effects of (6R)- and (6S)-tetrahydrobiopterin (BPH4), tetrahydroneopterin, and 6-methyltetrahydropterin on the activity of tryptophan hydroxylase were investigated in rat raphe slices. The activity of tryptophan hydroxylase was estimated by measurement of 5-hydroxytryptophan (5-HTP) formation under inhibition of aromatic L-amino acid decarboxylase with use of HPLC-fluorometric detection. (6R)-BPH4 (the naturally occurring form) at 42 microM, tetrahydroneopterin at 50 microM, and 6-methyltetrahydropterin at 100 microM increased tryptophan hydroxylase activity to 350, 145, and 146% of control values, respectively. (6S)-BPH4, however, had no significant effects on tryptophan hydroxylase activity. These results suggest that tryptophan hydroxylase is subsaturating in vivo for the naturally occurring cofactor, (6R)-BPH4, and that the concentration of (6R)-BPH4 may play an important role for the regulation of tryptophan hydroxylase activity in vivo.

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Studies on Tyrosine Hydroxylase System in Rat Brain Slices Using High-Performance Liquid Chromatography with Electrochemical Detection

Cited by 49 publications

References 19 publications

Dihydroxyphenylalanine Production in Rat Brain Striatal Synaptosomes: Stimulation by a Calcium Chelator

Dihydroxyphenylalanine Production in Rat Brain Striatal Synaptosomes: Stimulation by a Calcium Chelator

Biphasic actions of L‐DOPA on the release of endogenous noradrenaline and dopamine from rat hypothalamic slices

(6R)‐Tetrahydrobiopterin Increases the Activity of Tryptophan Hydroxylase in Rat Raphe Slices

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