Differential age-dependent effects of retinal deafferentation upon calbindin- and parvalbumin-immunoreactive neurons in the superficial layers of the rat's superior colliculus.

Several recent studies have reported varied effects of different forms of visual deprivation on the expression of calcium-binding proteins in the CNS. Most of these studies have surveyed only a single protein from this family and have not systematically evaluated the influence of the age of the animal upon the effects observed. The present study combined immunocytochemistry and quantitative morphometry to determine the effects of eye removal in fetal life, at birth, or in adulthood upon the expression of calbindin and parvalbumin by neurons in the retinorecipient laminae (the stratum griseum superficiale (SGS) and stratum opticum (SO)) of the rat's superior colliculus (SC). Both fetal and neonatal enucleation significantly reduced the total number of neurons in the SGS. Eye removal at any age did not significantly affect the number of neurons in the SO or the proportion of SGS or SO cells that expressed calbindin. Adult enucleation produced a significant increase in the percentage of SGS cells expressing parvalbumin. These results suggest that calbindin expression is highly stable in visual neurons while parvalbumin expression is more plastic and appears to be suppressed by retinal input.