The influence of two strains of Venezuelan equine encephalomyelitis virus on catecholamine metabolism in the central nervous system (CNS) of the mouse was studied by the intracranial inoculation of NMRI-IVIC mice, 24 days old. Doses of 300 LD50 of the moderately virulent Pixuna strain and 10(4) LD50 of the nonvirulent TC-83 strain were used. The animals were sacrificed 4, 7, 12, and 18 days after the inoculation, and the CNS contents of dopamine, norepinephrine, and adrenaline were determined by a radioenzymatic method. The turnover of these compounds was studied with the aid of the enzymatic inhibitors pargyline and alpha-methyl tyrosine. With the Pixuna strain a decrease in the level and turnover of catecholamines was observed in all eight brain areas studied: cerebellum, pons-medulla, hypothalamus, mesencephalon, striatum, olfactory bulb-tuberculum, hippocampus, and cerebral cortex. In some regions the levels returned to normal in 12-18 days, but in the striatum, mesencephalon, hypothalamus, and olfactory bulb-tuberculum, recovery was slower and required at least 18 days after inoculation. The levels of catecholamines in the brain of mice inoculated with the nonvirulent TC-83 strain were not modified, but there was a decrease in the turnover.
The activity of cholinesterase and its cellular and subcellular localization were investigated in the retina and optic tectum of Eugerres plumieri and in the retina of Carassius carassius by means of radiometric, histochemical, and cytochemical procedures. In both fishes only the presence of acetylcholinesterase could be demonstrated. This study, besides confirming previous findings that acetylcholinesterase is located in the ganglion and amacrine cells of the retina as well as in the inner plexiform layer, in addition provides evidence that the enzyme is also present at the region of photoreceptor synapses between the cell bodies and apposing extensions of the horizontal cells of the same layer. The latter localization may indicate the involvement of a cholinergic mechanism at the functional contacts (transferapses) between the horizontal cells. In the optic tectum of Eugerres plumieri, histochemistry reveals fine distinguishable bands of acetylcholinesterase activity; two of the bands are quite sharply defined, whereas three others have rather a more diffuse appearance. The presence of these bands and their distribution may suggest a widespread distribution of cholinergic elements in the optic tectum.
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