Regulation of calcium-binding protein immunoreactivity in GABA neurons of macaque primary visual cortex

Monocular deprivation produces an imbalance in visual drive from the two eyes, which in adult macaque V1 leads to marked changes in the neurochemistry of GABA interneurons. Such changes were further examined by studying immunoreactivity for calbindin, calretinin, and parvalbumin, three calcium-binding proteins that mark distinct subpopulations of GABA neurons, in macaques that had been monocularly deprived by intravitreal injection of tetrodotoxin. Deprivation for 5 d or longer produced a reversal in the normal pattern of calbindin immunostaining in layer III, from one in which intense neuronal immunostaining surrounded the cytochrome oxidase-rich puffs to one in which it occupied the puffs. Over the same period, calbindin immunostaining in other layers was reduced across the entire width of deprived-eye columns or extended into flanking regions of normal-eye columns. In contrast, reduction in parvalbumin immunostaining occurred only in deprived-eye columns and included only terminals with short periods of deprivation (up to 17 d) but both terminals and somata with longer periods. No change in calretinin immunoreactivity was observed. These findings demonstrate that GABA neurons of macaque V1 vary in their response to monocular deprivation according to their neurochemistry and position, suggesting that the weight of inputs from the two eyes and the intrinsic characteristics of each GABA population determine how a neuron responds to a change in visual input.