Myomodulin is present in two identified aplysia neurons that contain myomodulin A the ARC motor neuron B16 and the abdominal neuron L10. Ratios of myomodulin A to myomodulin B are approximately 6:1 in both cells. Like myomodulin A, myomodulin B potentiates ARC neuromuscular activity. It acts postsynaptically, and increases the size and relaxation rate of muscle contractions elicited either by motor neuron stimulation or by direct application of Ach to the ARC.