People in the Levine laboratory share a common interest in the function and development of neuromuscular systems. Neuromuscular systems, including the motoneurons that control movement and the muscles that they innervate, are modified throughout life by many factors including hormones, learning, training, and aging. We are using the molecular and genetic power of Drosophila and mammalian systems to explore the neural circuits that control movement and the mechanisms through which steroid hormones regulate their function and postembryonic modification. Using techniques such as intracellular and whole-cell patch recording, dye injection, confocal microscopy and cell culture we are describing the biophysical properties, dendritic anatomy, and synaptic connections of individual motoneurons. Recent experiments explore the role of calcium and potassium currents in determining the functional properties of identified motoneurons that participate in locomotor and respiratory behavior.