Abstract
Levels of radioactivity in various brain structures were measured after intraperitoneal injections of [ 3H]testosterone into adult male rats (castrated neonatally or in adulthood) and adult ovariectomized female rats (androgenized by neonatal testosterone injection or given control oil injection). (1) Brain structures concentrated radioactivity after [ 3H]testosterone injections to levels one to two times blood levels. In male rats castrated as adults, highest uptake was found in the pituitary, hypothalamus, preoptic area and septum. (2) The same pattern of uptake across brain structures was seen in the other treatment groups (neonatally castrated males and two group of females). However, neonatal castrates tended to accumulate less testosterone in all brain structures than the other treatment groups, and the pituitary of the adult-castrated male retained significantly more testosterone than in the other treatment groups. (3) Castrated prepuberal male rats showed a similar pattern of uptake across brain regions, compared to adult males, except for particularly high accumulation in the olfactory bulbs and lower accumulation in the brain stem. (4) Hypophysectomized castrated male rats accumulated less testosterone in all brain structures than castrated males with intact pituitaries. The hypophysectomy effect was largest in the preoptic area and septum and, in general, was larger in structures showing higher levels of uptake. (5) The percentage of radioactivity taken up as unchanged testorterone was greatest in the adult-castrated males and least in the neonatally-castrated males. This effect of sex difference and neonatal treatment was latent, and did not appear until after puberty. In all animals, brain regions showing competition effects were equivalent in percentage of unchanged testosterone to brain regions not showing competition effects. In adults, per cent unchanged testosterone was uniformly higher in the brain than in the blood.
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