BRAIN REGIONAL LEVELS OF NEUROTRANSMITTER AMINES AS NEUROCHEMICAL CORRELATES OF SEX-SPECIFIC ONTOGENESIS IN THE RAT

Brain regional levels of three neurotransmitter amines-serotonin (5-HT), norepinephrine (NE), dopamine (DA)-were measured in young rats prior to weaning to determine the extent to which modifications in levels of amines might reflect alterations in the sex steroid hormonal environment during the first postnatal week in the life of the rat. Sex-related levels of DA, NE, and 5-HT were found in some brain regions of the 12-day-old rat. Male midbrain DA exceeded the corresponding female value while female hypothalamic NE levels were greater than those of the male. Levels of 5-HT in the corpus striatum and the midbrain of males were greater than those of the female. Castration of the male on day 1 or testosterone propionate (TP) administration to the newborn female resulted in modifications of levels of midbrain 5-HT which reflected feminization of the castrated males and masculinization of the TP-treated females. Castration on day 1, or diethylstilbestrol given on days 2, 4, and 6, resulted in apparent feminization of NE levels in the hypothalamus of 12-day-old male rats. Thus, it appears that regional levels of hypothalamic NE and midbrain 5-HT in the 12-day-old rat may reflect the course of brain organizational activity which becomes recognizable in the adult as sex-specific behavior. © 1979 S. Karger AG, Basel.