Activitydependent Regulation Of Naag Expression

I examined NAAG immunoreactivity in the retina and LGN of monocularly deprived (MD) cats and compared it with that in normal cats.51, 52 As noted above, in the LGN of the normal cat, both the neuropil and the somata of relay cells are heavily labeled. Long-term monocular deprivation decreases labeling of the somata, but not the neuropil, in the deprived layers of the LGN (Fig. 5). There is little or no loss of label in the retinal ganglion cells of the deprived eye, as might be expected, given that the labeling of their terminals in the LGN is also unchanged. There is also no change in immunoreactivity for GAD, which is found in the interneurons of the LGN. The changes

Figure 5. Monocular deprivation alters NAAG levels in the lateral geniculate nucleus of the cat. The lids of one eye were sutured together before the time of natural eye-opening, and the animal was perfused as an adult. Lamina A is deprived on the left; lamina A1 is deprived on the right. Note the dramatic difference in intensity of staining between the deprived and non-deprived laminae. Affinity-purified antiserum.

Figure 5. Monocular deprivation alters NAAG levels in the lateral geniculate nucleus of the cat. The lids of one eye were sutured together before the time of natural eye-opening, and the animal was perfused as an adult. Lamina A is deprived on the left; lamina A1 is deprived on the right. Note the dramatic difference in intensity of staining between the deprived and non-deprived laminae. Affinity-purified antiserum.

in NAAG immunoreactivity of the LGN neurons in MD cats are much more striking than changes demonstrated with immunocytochemistry for glutamate, cytochrome oxidase histochemistry or uptake and incorporation into protein of 3H-leucine. Thus, the changes are unlikely to be due to an overall decrease in metabolism or protein synthesis. These results suggest that long-term monocular deprivation selectively decreases the synthesis of NAAG in geniculate neurons, or perhaps increases its hydrolysis. In contrast, 7-14 days of denervation is insufficient to reduce labeling in the cells of the cat's LGN.25

In the optic-chiasm sectioned monkeys, there was decreased cellular labeling for NAAG in the denervated ocular dominance columns.11 Similarly, 10 days after optic tract section in rats, cellular labeling in the ipsilateral cortex was reduced.26

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