Interaction of posttetanic potentiation and the catchlike property in mouse skeletal muscle

Introduction: Posttetanic potentiation (PTP) and the catchlike property (CLP) enhance contractile function in skeletal muscle. We investigated the CLP during dynamic performance in mouse hindlimb muscles with (wild-type) and without (skMLCK^-/-) the primary mechanism for PTP (myosin phosphorylation) (in vitro, 25°C). Methods: Extensor digitorum longus muscles of both genotypes were stimulated with constant frequency and catchlike trains (CFT and CLT), before and after a potentiating stimulus (PS). Results: Before the PS, the CLT increased concentric force/work relative to the CFT, but this effect was greater for skMLCK^-/- than wild-type muscles. After the PS, the catchlike effect was reduced in wild-type muscles but unchanged in skMLCK^-/- muscles that did not display PTP. Conclusions: These data suggest that PTP interferes with the CLP during concentric force development at moderate speeds of shortening. We conclude that the physiological utility of each mechanism and their interactions provide important modulations to fast skeletal muscle function. Muscle Nerve 54: 308–316, 2016.