EARLY ANDROGEN STIMULATION AND AGGRESSIVE BEHAVIOR IN MALE AND FEMALE MICE

The present series of experiments sought to determine the role of androgen in the neonatal mouse with respect to the development of brain mechanisms for aggression. Experiment 2 showed that male mice, and female mice given testosterone on the day of birth show comparable levels of aggression when gonadectomized and tested for fighting following testosterone administration in adulthood. Female mice treated with oil at birth, failed to show aggression in adulthood even when given large amounts of exogenous testosterone. A group of females given testosterone on the 10th day after birth showed more aggression than normal females, but less aggression than females given testosterone on the day of birth. Experiment 3 showed that mice castrated on the 10th day after birth and given testosterone as adults displayed significantly more aggression than mice castrated on the day of birth and similarly treated as adults. It was concluded that androgen stimulation of the mouse early in life causes the differentiation of a neural system for aggression which is more sensitive to androgen in adulthood than the system developing in the absence of neonatal androgenic stimulation. Experiment 1 showed that under the appropriate testing conditions, castrated male and female mice display aggression even in the absence of exogenous testosterone. © 1969.