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Neocortical Cholinergic Enzyme and Receptor Activities in the Human Fetal Brain
Author(s) -
Perry Elaine K.,
Smith Carthage J.,
Atack John R.,
Candy John M.,
Johnson Mary,
Perry Robert H.
Publication year - 1986
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.1471-4159.1986.tb00749.x
Subject(s) - acetylcholinesterase , choline acetyltransferase , medicine , endocrinology , cholinergic , pirenzepine , fetus , cerebral cortex , biology , muscarinic acetylcholine receptor , carbachol , receptor , cortex (anatomy) , chemistry , neuroscience , enzyme , biochemistry , pregnancy , genetics
In the human fetus, obtained postmortem at estimated gestational ages of 8–22 weeks, biochemical activities of cortical choline acetyltransferase (ChAT) and acetylcho‐linesterase (AChE) were comparable to those of adult brain tissue. In contrast cholinergic receptor binding, including muscarinic Ml and M2 subtypes (measured by displacement of [ 3 H] N ‐methylscopolamine with, respectively, pirenzepine and carbachol) and [ 3 H]nicotine (putative nicotinic) binding were undetectable before 13–14 weeks and even at 22 weeks were substantially (three‐ to fourfold) below the respective adult values. Cortical ChAT activity decreased significantly with gestational age whereas binding to the three receptors, including the proportion M1/M2, increased significantly. AChE was present at all ages investigated as the two molecular monomeric (G1) and tetrameric (G4) forms. The proportion of G4, which was much more soluble in fetal compared with adult cortex, increased approximately threefold. Histochemically AChE, although intense in the nucleus of Meynert, was generally confined to subcortical white matter at early fetal developmental periods, appearing later in the cortex localized to nerve fibres and occasional cell bodies. These observations suggest that during the second trimester of human fetal development, cortical cholinergic function may be preceded by relatively high ChAT activity and paralleled not only by increasing receptor binding but also by a proportional increase in the tetrameric form and histochemical reactivity of AChE.