Myomodulin is a neuropeptide present in molluscs, insects, and gastropods. In Vitro: Myomodulin decreases period and increases spike frequency in oscillator heart interneurons. Myomodulin enhances the hyperpolarization-activated cation current and inhibits the electrogenic Na/K pump^[1]. A myomodulin peptide has been suggested to mediate the response of the giant glial cells to stimulation of the Leydig interneuron in the central nervous system of the leech Hirudo medicinalis. The peptide evokes a membrane outward current (EC₅₀ approximately 2 μM), which neither desensitizes nor shows any sign of run-down, and elicits a K⁺ conductance increase of the glial cell membrane^[2]. Myomodulin modulate ion channels in a wide variety of organisms including Aplysia, Lymnaea, and Pleurobranchaea. Myomodulin differentially modulates the potassium currents and reduces the amplitude of the Ca²⁺ current by 20%^[3].