Sex difference in neuronal loss induced by axotomy in the rat brain stem motor nuclei.

The magnitudes of axotomy-induced neuronal loss in male, female, and castrated male rats were compared. Ten to twelve weeks after unilateral transection of the hypoglossal and facial nerves in rats of 3 and 6 weeks of age, a significant reduction in cell number occurred in the axotomized motor nuclei. The cell loss was two times greater in females and male castrates than in males, suggesting that higher levels of androgens in males attenuated neuronal loss. The time course of neuronal loss in females axotomized at 6 weeks of age was followed. Results indicated that the neuronal population on the axotomized side sustained a gradual decline during the 1- to 12-week postaxotomy periods, being reduced eventually by 25-30%. No further cell loss was evident thereafter up to 20 weeks postaxotomy. The present study demonstrates that androgens can influence motoneuron survival not only during development as shown by E. J. Nordeen, K. W. Nordeen, D. R. Sengelaub, and A. P. Arnold (1985, Science 229: 671-673) but also in adulthood.