AJP - Gastrointestinal and Liver Physiology, Vol 244, Issue 1 58-G64, Copyright © 1983 by American Physiological Society
Development of neurotransmitter enzyme activity in the rat gastrointestinal tract
M. M. Heitkemper and S. F. Marotta
Acetylcholine and norepinephrine play important roles in determining
gastrointestinal (GI) tract motility and secretion. At this time, however,
little is known concerning the postnatal developmental patterns of the
enzymes that synthesize and degrade these two neurotransmitters within the
GI tract. The present study examined the developmental activities,
expressed per gram protein per minute, of the cholinergic enzymes choline
acetyltransferase (ChAT) and acetylcholine esterase (AChE) and the
adrenergic enzymes tyrosine hydroxylase (TH) and monoamine oxidase (MAO) in
male rats between days 1 and 50. Seven anatomic segments of the GI tract
were assayed for enzyme activities. In general, all four neurotransmitter
enzymes were present throughout the length of the GI tract and increased
during the early postnatal period. The synthesizing enzymes ChAT and TH
displayed peak activity prior to day 21, while the degrading enzymes AChE
and MAO continued to increase past day 21. Each enzyme exhibited segmental
differences and unique postnatal developmental patterns. Such differences
in enzyme activities may be related to developmental increases in neuronal
density, hormonal factors, or direct stimulation of the GI tract by liquid
and/or solid diet.
