Parvalbumin and calbindin immunoreactivity in the rat brain: a double-immunolabelling method.

Parvalbumin and calbindin, two calcium binding proteins in the nervous system, are present in certain neuronal subpopulations. In the present study a method for a simultaneous demonstration of the both antigens was developed, which labels parvalbumin- and calbindin-containing structures in contrasting colours. A horseradish peroxidase-conjugated second antibody was used for the visualization of the monoclonal anticalbindin antibody, whereas the biotinylated anti-parvalbumin antibody was demonstrated by means of a biotin-streptavidine-alkaline phosphatase system. The method may be useful to classify neuronal populations and to study their morphological relationship.