Immunosuppressant FK506 prevents mossy fiber sprouting induced by kindling stimulation

Kindling stimulation induces expansive growth of the axons of the dentate granule cells; the messy fiber, into several areas of the hippocampus. An intraperitoneal injection of the immunosuppressant drug FK506, which is a specific inhibitor of Ca2+-calmodulin dependent phosphatase, calcineurin, prevented the full development of kindling as well as messy fiber sprouting. The results show a correlation between messy fiber sprouting and the development of kindling. The results suggest also that calcineurin may have a promoting role in messy fiber sprouting and subsequent synaptogenesis.