The effects of neonatal androgenization on the in vivo transport of alpha-aminoisobutyric acid into specific regions of the rat brain

Abstract

The purpose of the present study was to determine if the administration of testosterone propionate (TP) to neonatal rats is followed in vivo by alterations in the transport of the non-metabolizable amino acid, α-aminoisobutyric acid (AIB), into specific regions of the brain. Forty-eight hours after birth, male and female rats were injected s.c. with either 1.25 mg TP or an equivalent volume of vehicle. Five, 10 and 17 days after birth, control and TP-treated rats were decapitated at intervals of 2, 5, 60 and 300 min after the i.p. injection of 0.25 μCi [1- 14C]α-aminoisobutyric acid/g body weight. Twelve brain regions, i.e., amygdala, cerebellum, corpora quadrigemina, frontal cortex, hypothalamus, medulla, occipital cortex, olfactory bulbs, olfactory tubercles, parietal cortex, pons, pyriform cortex and samples of serum were analyzed in terms of disint./min/mg tissue and as tissue/serum (T/S) ratios. At the end of 300 min there was a significant increase in the active transport of AIB in all brain regions of the 5-day-old TP-treated rats. Similarly, by 300 min, the active transport of AIB was significantly increased in all brain regions except cerebellum and pons of the 10-day-old TP-treated rats. The administration of TP to neonatal rats did not alter the accumulation and/or active transport of AIB in brain regions of the 17-day-old rat at any of the tested intervals. These data indicate that (1) neonatally administered TP enhanced (either directly or indirectly) the transport and/or accumulation of AIB in specific brain regions of 5- and 10-day-old rats and (2) the effectiveness of the steroid decreased with the age of the rat.