DARK REARING and VISUAL STIMULATION IN THE RAT: EFFECT ON BRAIN ENZYMES

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Abstract
Abstract— Enzyme activities in motor and visual cortex and cerebellum of rats reared for 50 days in the dark (D) were compared to levels in normally reared (N) and in dark‐reared littermates exposed to 3 h of visual stimulation (L). Amongst 6 acid hydrolases, two, acid phosphatase and galactosaminadase, showed no effect of dark rearing. In three of the others, glucuronidase, glucosaminidase and galactosidase, activity tended to be lower in D than L. In glucosaminidase, N was similar to D and L above both, while in (total) glucosidase, galactosidase and glucuronidase, N was higher than D and L approached N. There were fewer changes in cerebellum than in cortex.Visual cortex acetylcholinesterase was 29% higher in L than in D, and 41% higher in L than in N, but there were no significant differences in AChE or BChE in motor cortex or cerebellum. Choline acetyltransferase was higher by 30% in L and D in visual cortex, and 22% in motor cortex. There were no differences in the cerebellum. There were no differences in the levels of activity of glutamate decarboxylase or Na+, K+, Mg2+ ‐ATPase in any region or condition.The significance of both the apparently transient and more permanent effects of dark rearing and light exposure on the enzymes studied, and discrepancies with other reports of enzyme changes in dark rearing are discussed.