We propose to study the organization and control of the central pattern generator for locomotion using the isolated lamprey spinal cord as our model system. In particular, we hope to understand the 1) neural control of the inter-segmental coordination, 2) the interrelation between the fin and the body muscle, and 3) the role in the control of the pattern generator by serotonin. To study the coordinating system and fin control, we will combine standard neurophysiological experimental techniques with a mathematical treatment which includes dynamical systems and non-linear oscillator theory. To study the role of serotonin, we will first determine the appropriate serotonergic antagonist for the lamprey cord. We can then attempt to block various functions we feel may be serotonin-mediated. Study of the vertebrate generation and control of locomotion is extremely difficult in higher more complex nervous systems. In this simple nervous system we hope to deduce general principles which will apply throughout the vertebrates.