Catecholamine Enhancement and Visual Cortex Plasticity in Developing Kittens

摘要

We attempted a test of the hypothesis that the naturally occurring catecholamines are necessary to support experience-related changes in cortical neurons. Four kittens were reared in absolute darkness for 9-16 weeks and subsequently given varying periods (3 hours to 3 weeks) of monocular experience through the left eye. In three kittens, (K84, K85, K92) osmotic minipumps maintained local perfusion of norepinephrine (NE) into the left hemisphere area 17 while a control solution perfused the corresponding region of the right hemisphere. A fourth kitten underwent 6-hydroxydopamine induced catecholamine depletion followed by NE replacement in one hemisphere. It was given monocular experience during replacement therapy. We used standard single unit recording techniques to sample from primary visual cortex neurons. Results of liquid chromatography analysis for NE in samples of brain tissue were inconclusive because of small sample sizes. In general, our results indicate that ocular dominance and selectivity of individual neurons was not significantly affected by enhanced levels of NE. However, selectivity did show a dependence on depletion of NE in one kitten. (Author)