Superfast fish show superfast coupling

Abstract

JGP study reveals that adult zebrafish skeletal muscle fibers display the fastest kinetics of excitation-contraction coupling ever measured in vertebrate locomotor muscles.

Romane Idoux (left), Bruno Allard (center), and colleagues demonstrate the superfast kinetics of EC coupling in adult zebrafish skeletal muscle fibers that allow the muscles to contract when excited at extremely high frequencies, powering the animal’s rapid startle response. When stimulated at 200 Hz for 0.5 s, zebrafish fibers form a fused and sustained Ca²⁺ transient (left trace), whereas in a mouse fiber excited at the same rate (right trace), the initial Ca²⁺ transient quickly returns to baseline because the second stimulation of the train fails to trigger an action potential (inset).