Postnatal development of tail motoneurons and muscles in cat

The postnatal development of motoneurons in two tail muscles, the extensor caudae medialis (ECM) and extensor caudae lateralis (ECL), and that of ECL muscle fibers were studied in cats 1 week to 2 months old. The location of ECL and ECM motoneurons in cats of different ages did not change postnatally. Somal size (average of maximal and minimal diameters) of ECL and ECM motoneurons gradually increased, and the size distribution of ECL was bimodal at 2 months. The activities of succinate dehydrogenase (SDH) and phosphofructokinase (PFK) were studied to determine oxidative and glycolytic activities in ECL growth. SDH activity rapidly decreased between 1 week and 2 weeks of age, while PFK activities increased gradually.