Parvalbumin (PV) is a calcium binding protein expressed in specific muscle fibers and fast-firing neurons. PV consists of a single, unbranched chain of linked amino acids and belongs to a larger group of EF hand proteins. Studies have demonstrated that parvalbumin acts in the decay of calcium in the contraction/ relaxation cycle of fast twitch muscles. This data has shown a positive correlation between the rate of relaxation and the concentration of parvalbumin. Parvalbumin is also expressed in a specific population of GABAergic interneurones which are thought to play a role in maintaining the balance between excitation and inhibition in the cortex as well as the hippocampus. In amyotrophic lateral sclerosis (ALS) patents, parvalbumin immunoreactivity is specifically absent from neuron populations lost early in ALS.
