Gopal D. Das

Behavioral manipulations and protein metabolism of the brain: Effects of motor exercise on the utilization of leucine-H3

Abstract The utilization of systemically injected leucine-H 3 by nerve cells was investigated autoradiographically in exercised and unexercised rats. Handled rats reared in an enriched environment were run daily for a long period in a motor-driven exercise wheel to adapt them to forced exercise. On the day of administration of the radiochemical the “exercised” animals were forced to run for 1 hr prior and 1 hr after the injection, whereas the “unexercised” animals rested before and after injection. Microdensitometric evaluation of autoradiographic grain density over single nerve cells in several brain regions indicated that there were no significant differences in the utilization of the radiochemical by proteins of the brain in the two groups of animals, though there was a slight trend of increased incorporation of leucine-H 3 in the exercised group of animals. The results suggest that the presumed functional activation of the brain by this sensori-motor task need not lead to enhanced protein metabolism if the stress produced by forced exercise is reduced or eliminated by pre-adaptation to the task.

Behavioral manipulations and protein metabolism of the brain: Effects of visual training on the utilization of leucine-H3

Abstract The utilization of systemically injected leucine-H 3 by the brain was compared in visually-deprived rats and rats receiving prolonged training in a maze on a series of visual pattern-discrimination tasks. Microdensitometric evaluation of autoradiographic grain density over single nerve cells in a variety of visual and nonvisual brain regions indicated that there was no significant difference in the utilization of the radiochemical by proteins of the brain in the two groups of animals; though there was a trend of increased uptake in several visual and nonvisual structures in the visually-deprived animals. This result supports our previous conclusion that the presumed functional activation of the brain by behavioral engagement need not lead to increased protein metabolism, as measured by our technique. The slight increase in the utilization of leucine-H 3 in the visually-deprived animals can be attributed to the greater stress produced by the injection procedure in these unhandled animals.

Behavioral manipulations and protein metabolism of the brain: Effects of restricted and enriched environments on the utilization of leucine-H3

Abstract The utilization of systemically injected leucine-H 3 by nerve cells was investigated autoradiographically in rats reared in a restricted and enriched environment. Microdensitometric evaluation of autoradiographic grain density over single nerve cells in several brain regions indicated a significant increase in the utilization of the radiochemical by proteins of the brain in the restricted group of animals. This finding supports the hypothesis that the presumed activation of neuronal circuits by chronic behavioral engagement, represented by the enriched environment, need not lead to enhanced protein metabolism; instead, it is the stress produced by handling and the injection procedure in the previously unhandled, restricted animals that leads under these conditions to increased utilization of the labeled precursor of proteins.