PD 90780 is a selective inhibitor of calcineurin, a protein phosphatase involved in various cellular signaling pathways. It is primarily used in research and development to study calcineurin-dependent processes, such as NFAT dephosphorylation and activation in T-cells and neurons. In laboratory settings, it is employed to investigate its effects on synaptic plasticity, dendritic spine morphology, and neuronal signaling, particularly in the context of learning, memory, and neurodegenerative diseases. Its applications are confined to experimental studies, with potential implications for therapeutic development targeting calcineurin dysregulation in neurological and immunological disorders.