Calbindin D-28K and parvalbumin immunoreactivity is confined to two separate neuronal subpopulations in the cat visual cortex, whereas partial coexistence is shown in the dorsal lateral geniculate nucleus.

Calbindin D-28K-immunoreactive cells were localized in the supragranular layers of the striate cortex of the cat, while parvalbumin-stained cells occurred from the bottom half of layer II through layer VI, making the two distributions almost complementary. Calbindin- and parvalbumin-positive cells occurred throughout the 3 layers of the dorsal lateral geniculate nucleus (dLGN), but calbindin-immunoreactive cells outnumbered parvalbumin-positive cells. Double labeling on single sections was performed in order to determine the possible coexistence of calbindin and parvalbumin in single cells of cat visual cortex and dLGN. Calbindin and parvalbumin immunoreactivity was found in two separate neuronal populations in the visual cortex, while in the dLGN about 50% of the cells were doubly stained.