Testosterone recruits new aromatase-imunoreactive cells in neonatal quail brain

Abstract

It was shown earlier that, in Japanese quail the mechanism controlling the induction by testosterone of aromatase activity develops between embryonic days 10 and 14. The cellular processes underlying this activation have, however, not been investigated in detail. Here, we demonstrate that the increase in aromatase activity observed in neonates treated with testosterone propionate between postnatal days 1 and 3 results from the recruitment of additional populations of aromatase-immunoreactive cells that were not expressing the enzyme at detectable levels before. This recruitment concerns all brain nuclei normally expressing the enzyme even if it is more prominent in the ventromedial hypothalamus than in other nuclei.

Fig. 1

Effects of two injections of 1 mg testosterone propionate (TP) on brain aromatase activity in three-day old male (black) and female (gray) quail. ***= p<0.0018 by comparison with the oil injected controls.

Fig. 2

Distribution of ARO-ir cells and effect of testosterone propionate (2×1mg TP) on the number of immunopositive cells in three-day old quail. A–B. Low magnification photomicrographs of coronal sections in brains of male chick that had been treated with TP (right) or oil as a control (left). The drawings on the left present a schematic view of the nuclei location in the brain (boxes) corresponding to the photographs. C–H. Photomicrographs at higher magnification of the medial preoptic nucleus, POM (C–D), rostral nucleus of the stria terminalis, BSTM (E–F) and ventromedial hypothalamus, VMH (G–H) of oil-treated (C, E, G) or TP-treated (D, F, H) males. Abbreviations: ac, anterior commissure; dso, supraoptic decussation; Mes, mesencephalon; PAG, periaqueductal gray; pc, posterior commissure; POA, preoptic area; PVO, periventricular organ; OT, optic tectum; ot, optic tract; Se, septum; Tel, telencephalon; III, third ventricle. Scale bar = 600 µm in A-B, 75 µm in C–H (shown in G only).

Fig. 3

Effect of testosterone propionate (2 × 1mg TP) on the number of ARO-ir cells in the medial preoptic nucleus (POM), ventromedial hypothalamus (BSTM) and ventromedial hypothalamus (VMH) of male (black) and female (gray) quail. *= p<0.05 and ***= p<0.001 by comparison with oil-injected control subjects. No sex difference and no interaction of sex with endocrine treatment were detected.