text: IP's main functions are to mobilize Ca from storage organelles and to regulate cell proliferation and other cellular reactions that require free calcium. In smooth muscle cells, for example, an increase in concentration of cytoplasmic Ca results in the contraction of the muscle cell.
  In the nervous system, IP serves as a second messenger, with the cerebellum containing the highest concentration of IP receptors. There is evidence that IP receptors play an important role in the induction of plasticity in cerebellar Purkinje cells.