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HISTAMINE FORMATION IN RAT BRAIN IN VIVO : EFFECTS OF HISTIDINE LOADS 1 2
Author(s) -
Schwartz J. C.,
Lampart C.,
Rose C.
Publication year - 1972
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1972.tb01394.x
Subject(s) - histidine decarboxylase , histamine , histidine , histamine n methyltransferase , cycloheximide , in vivo , carboxy lyases , chemistry , hypothalamus , endocrinology , decarboxylase inhibitor , medicine , enzyme , biochemistry , biology , histamine h2 receptor , protein biosynthesis , antagonist , levodopa , receptor , microbiology and biotechnology , disease , parkinson's disease
— Administration of l ‐histidine at the rate of 500 mg/kg induced an increase of nearly 50 per cent in the level of histamine in rat brain which lasted several hours. The augmentation of histamine level was not significant 3 h after lower doses or after d ‐histidine α‐methyl DOPA and Ro 4‐4602 neither affected the cerebral level of histamine nor its elevation induced by l ‐histidine. Brocresine, a known histidine decarboxylase inhibitor not only prevented the effect of histidine load but also induced a prompt fall in the amine level. These results confirm those from earlier experiments in vitro indicating that histamine synthesis in rat brain depends on a specific decarboxylase (EC 4 , 1.1.22) which is not normally saturated by the endogenous level of its substrate. When histamine levels were enhanced by histidine treatment, histidine decarboxylase activity, as evaluated on hypothalamus homogenates, was significantly reduced; intracisternal administration of cycloheximide, an inhibitor of protein synthesis, had similar effects. On the other hand, enzyme activity was not altered by the addition of histamine to hypothalamus homogenates. These results are compatible with the existence of a regulation mechanism of histidine decarboxylase involving repression by its end‐product.