Density of SMI-32 immunopositive neurons in eye-specific layers of lateral geniculate nucleus in kittens reared with monocular deprivation and unilateral convergent squint.

The non-phosphorylated heavy neurofilament proteins, which can be labelled by SMI-32 antibodies, are characteristic for large, fast-conducting neurons. In the visual system, such properties are typical for Y-neurons. It is known that in monocularly deprived or squinting animals the Y-neurons population declines in A-layers of lateral geniculate nucleus (LGNd), connected with a deprived/squinting eye. However if this loss depends on eccentricity of the visual field projection is still not known. To study this, as well as the time course of the developmental changes, we used the frontal sections of LGNd of both hemispheres of 2- and 3- month kittens reared with monocular deprivation or unilateral convergent squint. We had developed the custom software to divide the binocular part of A-layers into 10 consecutive sectors and to calculate the number of SMI-32 immunopositive neurons in each of them. The neuronal density was calculated and compared between groups in sectors with the same eccentricity. In monocularly deprived animals, decline of the neuronal density relative to the control group was found in layers, innervated from the deprived eye in both age groups, regardless of eccentricity. However in strabismic kittens the decrease in neuronal density was revealed only in the peripheral sectors of layer A1, driven by deviated eye. The width of this area of reduced Y-neuron density was larger in 3 months kittens, indicating that the development of the disorder has not yet stabilized. The results may be interpreted as morpho-physiological correlates of different types of human amblyopia.