Effects of low calcium and inhibition of calcium-activated neutral protease (CANP) on mature nerve terminal structure in the rat sternocostalis muscle.

The possible role of calcium and a calcium-activated neutral protease (CANP) in the reorganisation of mature mammalian neuromuscular junctions was studied in the sternocostalis muscle in rats. After the well-documented loss of polyneuronal innervation has occurred, the remaining single mature nerve ending continues to change its terminal branching pattern by gradually becoming more complex. Reducing local calcium concentrations by the chelating agent BAPTA or inhibiting CANP by local application of an inhibitor, Leupeptin, resulted in the endings becoming more complex in appearance when examined after 6 or 7 days. It is concluded that calcium and CANP are important in the remodelling of mature neuromuscular junctions.