ISSN:
1420-908X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The activity of histidine-decarboxylase (HD) and histamine-N-methyl-transferase (HMT) was studied in the hypothalamus and cerebral cortex of rats from birth to adulthood. Development patterns were compared in sea-level controls and in rats born and maintained continuously in a natural hypoxic environment (at a high altitude of 3800 m, PO 2 13%) to determine whether chronic stress alters the development of the enzymes for histamine. When expressed in terms of total activity, both enzyme activities were low at birth and progressively increased with age in the two areas studied. When expressed in terms of specific activity, the developmental pattern of the enzymes better reflected that of histamine: for example, at birth, high HD activity and low HMT corresponded to high histamine levels; at 7 days, low HD activity and high HMT corresponded to low histamine levels. It is suggested that a feedback mechanism may operate between endogenous histamine levels and the activity of its synthesizing and catebolizing enzymes. Exposure to chronic stress failed to alter enzymatic activity during the first postnatal week, but significantly influenced it in later development and adulthood. In the hypothalamus stress induced HD activity in the developing animals but depressed it in the adults. In the cerebral cortex, HMT rather than HD was stimulated by stress, but here again the effects were age-dependent. The sensitivity of histaminergic enzymes to environmental stimulation provides indirect supportive evidence for neurotransmitter role of histamine.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01966849