Triple innervation of the crayfish opener muscle: the astacuran common inhibitor.

Part of the much-studied crayfish opener muscle receives a second inhibitory input in addition to its well known specific excitatory and inhibitory innervation. This second inhibitor, formerly thought to innervate only four of the seven peripheral leg muscles, is in fact a common inhibitor of all seven. This has significance both for previous findings in this muscle and for the role of the common inhibitor in decapods.