Localization and soma diameter of rat gluteus medius motoneurons.

1. Retrograde transport of horseradish peroxidase was used to examine the localization and soma diameter of motoneurons innervating the deep (predominance of oxidative fibers) and superficial (predominance of non-oxidative fibers) portions of the gluteus medius muscle in rats. 2. The motoneurons innervating the deep portion were located caudally within the gluteus medius motoneuron pool and had smaller average soma diameter than that of motoneurons innervating the superficial portion. 3. These results suggest that the location of the muscle fibers within the muscle is related to the location of motoneurons within the motoneuron pool, and that the soma diameter of motoneuron innervating oxidative muscle fibers may be smaller than those innervating non-oxidative fibers in the rat.