Effects of chronic monocular enucleation on calcium binding proteins calbindin-D 28k and parvalbumin in the lateral geniculate nucleus of adult rhesus monkeys

Abstract

The calcium binding proteins parvalbumin and calbindin-D 28k were localized immunocytochemically within the lateral geniculate nucleus of adult monkeys at 1–7 months after monocular enucleation. Within the deafferented magno- and parvocellular layers, parvalbumin and calbindin-D 28k immunoreactive fibers were depleted at all post-enucleation times. The neuronal staining for parvalbumin was similar in numerical density and intensity between the deafferented and intact layers. In hemispheres examined at 5 and 7 months post-enucleation, parvalbumin-immunoreactive fibers were also lost within the deprived ocular dominance bands in layers IVA, IVC and VI of the visual cortex, suggesting that cellular expression or axonal transport of parvalbumin may be decreased in the deafferented geniculate laminae. While the intact magno- and parvocellular layers contained very few neurons that were immunoreactive for calbindin-D 28k, the density of calbindin-D 28k-positive neurons increased in these layers after deafferentation. The counts of calbindin-D 28k and parvalbumin immunostained neurons were not statistically different at 4–7 months post-enucleation. Because virtually all magno- and parvocellular projection neurons express parvalbumin, many parvalbumin neurons that normally do not contain calbindin-D 28k may co-express this in response to injury. The findings suggest that long-term deafferentation imposes additional calcium buffering requirements on lateral geniculate neurons.