MORPHOLOGICAL CHANGES IN THE BRAINS OF ADULT MALE RATS AFTER NEONATAL CASTRATION

Abstract

Male rats castrated shortly after birth respond to testosterone injections in adulthood with an incomplete pattern of masculine mating behaviour (Beach & Holz, 1946; Gerall, 1958; Harris, 1964; Grady, Phoenix & Young, 1965) and display elements of female sexual behaviour more frequently than males castrated in adulthood (Harris, 1964; Feder & Whalen, 1965; Grady et al. 1965). A search was made for structural differences in the brain which might correspond to these persisting behavioural effects of neonatal castration. Four male rats were anaesthetized and castrated 7 days after birth and were then treated like their normal litter-mates, three males and two females. The nine animals were killed when 126 days old. Histological and sampling procedures were the same for all brains. Cross-sectional areas of the brain and brain structures were determined by planimetry on tracings of their magnified images. Also, cells were counted in some parts of the brain. The