POSTNATAL-DEVELOPMENT OF TAIL MOTONEURONS AND MUSCLES IN CAT

The postnatal development of motoneurons in two tail muscles, the exte nsor caudae medialis (ECM) and extensor caudae lateralis (ECL), and th at of ECL muscle fibers were studied in cats 1 week to 2 months old. T he location of ECL and ECM motoneurons in cats of different ages did n ot change postnatally. Somal size (average of maximal and minimal diam eters) of ECL and ECM motoneurons gradually increased, and the size di stribution of ECL was bimodal at 2 months. The activities of succinate dehydrogenase (SDH) and phosphofructokinase (PFK) were studied to det ermine oxidative and glycolytic activities in ECL growth. SDH activity rapidly decreased between 1 week and 2 weeks of age, while PFK activi ties increased gradually.