Showing papers by "Patrick L. McGeer published in 1967"

Some characteristics of brain tyrosine hydroxylase

Abstract: There is general agreement as to the properties of tyrosine hydroxylase from the adrenal medulla, but the properties of brain tyrosine hydroxylase are more controversial. This is perhaps not so surprising when one considers that the adrenal medullary cells are secretory cells which do not possess the long axons and multiplicity of nerve endings characteristic of central catecholaminergic neurons. The relatively complex structure of the neuron has complicated the problem of defining the properties of brain tyrosine hydroxylase and will probably prove important to an understanding of the factors which control or modify enzyme activity in vivo.

Distribution of tyrosine hydroxylase activity in adult and developing brain.

Abstract: The distribution of tyrosine hydroxylase activity in various areas of brain was studied in mature rats, rabbits, cats, and in kittens of various ages. Distribution was closely similar in all species. Areas known to have high concentrations of catecholinergic nerve endings, such as the caudate, septal area and pineal, showed very high adult levels and sharp increases during the neonatal period. Areas such as the pons–medulla and midbrain, known to contain predominantly catecholinergic cell bodies, showed, on the other hand, relatively low adult levels and little or no change in the neonatal period. Developmental data correlate with known neonatal changes in endogenous catecholamine levels and adult distributions correlate with known turnover rates. The results are in conformity with previous findings that tyrosine hydroxylase is concentrated largely in nerve endings and suggest that measurement of this enzymic activity may provide a more convenient and more sensitive index of catecholinergic nerve activity...