Metabolic changes in axotomized fetal and early postnatal hamster facial motoneurons: an autoradiographic study.

The developing facial neurons of a series of hamsters ranging in age from the 14-day fetus to the 9 day postnatal were axotomized. Postoperative times were graded for each age so that the retrograde response could be observed before any significant amount of cell degeneration or death occurred. The incorporation of tritiated uridine was followed by the autoradiographic procedure. Although grain counts, relative to control values, were significantly reduced only in the axotomized fetus and at 24 hours postoperatively in 4-day postnatal animals, there was also a repression of isotopic incorporation in all the other axotomized animals. These results support data obtained from previous work with the hamsters which indicate that it is not until after the nerve cell nucleolus reaches full cytomorphic maturity (between 15 and 20 days postnatal age in hamster facial neurons) that the axotomized neurons respond with significantly increased incorporation levels of isotope over that of control neurons.