Calcium-binding proteins calbindin D28K, calretinin, and parvalbumin immunoreactivity in the rabbit visual cortex

The distribution and morphology of neurons containing three calcium-binding proteins, calbindin D28K, calretinin, and parvalbumin in the adult rabbit visual cortex were studied. The calcium-binding proteins were identified us ing antibody immunocytochemistry. Calbindin D28K-immunoreactive (IR) neuron s were located throughout the cortical layers with the highest density in l ayer V. However, calbindin D28K-IR neurons were rarely encountered in layer I. Calretinin-IR neurons were mainly located in layers II and III. Conside rably lower densities of calretinin-IR neurons were observed in the other l ayers. Parvalbumin-IR neurons were predominantly located in layers UT, IV V , and VI, In layers I and II, parvalbumin-IR neurons were only rarely seen. The majority of the calbindin D28K-IR neurons were stellate, round or oval cells with multipolar dendrites, The majority of calretinin-IR neurons wer e vertical fusiform cells with long processes traveling perpendicularly to the pial surface. The morphology of the majority of parvalbumin-IR neurons was similar to that of calbindin D28K: stellate, round or oval with multipo lar dendrites, These results indicate that these three different calcium-bi nding proteins are contained in specific layers and cells in the rabbit vis ual cortex.