Quantitative analysis of the postnatal axon growth in the dorsal funiculus of rats

The dorsal funiculus in cervical spinal cords of rats from birth to 120 days postnatally has been studied on order to document the axon growth. Within the dorsal funiculus the cuneate and gracile fasciculi have been examined and within the gracile fasciculus the distinct cervical, thoracal and lumbar areas. Light microscopy and morphometry on the day of birth and 15, 20 and 120 days postnatally show an axon growth stagnation between the 15th and 20th day of maturation. The stagnation phase seems to induce the myelinization. A comparison between Goll's and Burdach's tracts shows an earlier and faster growth of the axons in Burdach's tract. Consequently, the epicritical sensibility of the upper extremity is developed earlier. It has been found out that within Goll's tract a caudocranial maturation takes place. The lumbar area of the fasciculus gracilis is matured earlier than the thoracal and the cervical ones.