Parvalbumin

Parvalbumin is expressed in fast-contracting muscles, where its levels are highest, as well as in the brain and some endocrine tissues. In brain, it is particularly concentrated in Purkinje cells and interneurons in the molecular lay, but is also found in many GABAergic interneurons in the cortex. These GABAergic interneurons in most cases express only one of three Ca2+ binding proteins, namely parvalbumin calretinin, or calbindin. As a result, these important inhibitory interneurons can be identified and subclassified based on their content of these three proteins and antibodies to these three proteins are useful for identifying specific neuronal cell types. Each type of neuron as defined in this fashion has particular electrophysiological and functional properties. For example, calbindin positive interneurons are not fast-spiking as are parvalbumin expressing interneurons.