The differences in the neuronal metabolic activity in eye-specific layers of the dorsal lateral geniculate nucleus in cats with altered binocular vision
In order to study the changes in visual subcortical structures caused by early binocular vision impairments, the neuronal functional activity of the dorsal lateral geniculate nucleus (LGNd) was evaluated in monocularly deprived cats and cats with strabismus, caused by eye muscles tenotomy. The histochemical method was used to detect the cytochrome oxidase (CO) - the mitochondrial enzyme of respiratory chain, which activity level correlate to the neurons functional activity. The optical density in ocular-specific layers A and A1 was measured on the images of the LGNd stained sections in the projection of central 5 deg., and the contrast was calculated between the optical densities in these layers. It was found that in monocularly deprived cats the contrast value in the hemisphere contralateral to deprived eye was negative, and in the hemisphere ipsilateral to deprived eye was positive. These hemispheric differences of the K values were also observed in cats with unilateral (convergent and divergent) strabismus, as well as in cats with bilateral strabismus. Absolute value of K in the cats with impaired binocular vision was significantly higher than in the intact cats, whose difference K from zero was determined by the dominance of the one eye. We suggest that the observed differences in optical density between layers A and A1 of the LGNd are due to reduced functional activity of neurons that receive inputs from the deprived or strabismic eye. Such differen§ces observed in bilateral strabismus also suppose a decreased activity of the one eye.