Parvalbumin is a low molecular weight cytoplasmic Calcium binding protein containing the “EF hand” Calcium binding motif and is the first protein characterized in this subclass. Parvalbumin is expressed in fast-contracting muscles, in the brain and in some endocrine tissues. In brain it is particularly concentrated in Purkinje cells and interneurons in the molecular layer, but is also found in many cortical GABAergic interneurons. These GABAergic interneurons in most cases express only one of three Calcium binding proteins, namely parvalbumin, calretinin or calbindin. Each type of interneuron has distinct electrophysiological properties and as a result, different types of interneuron can be identified and classified based on their content of these three proteins. The Pvalb antibody was made against full length recombinant human parvalbumin expressed in and purified from E. coli. Since parvalbumin is related in amino acid sequence to both calretinin and calbindin, we also expressed these proteins to check that our various reagents show no cross reactivity. So our antibodies to parvalbumin are useful cell type markers provided, as is the case with this antibody, they do no cross react with the related molecules calretinin or calbindin.