Region‐specific expression and sex‐steroidal regulation on aromatase and its mRNA in the male rat brain: Immunohistochemical and in situ hybridization analyses

Abstract

The brain has an estrogen-biosynthetic potential resulting from the presence of neuronal aromatase, which controls the intraneural sex-steroidal milieu and is involved in brain sexual differentiation, psychobehavioral regulation, and neuroprotection. In the rat brain, three distinct aromatase-P450-immunoreactive (AromP450-I) neural groups have been categorized in terms of their peak expression time (fetal, fetoneonatal, and young-to-adult groups), suggesting the presence of region-specific regulation on brain AromP450. In the present study, we compared the expressions between AromP450 protein and mRNA by using immunohistochemistry and in situ hybridization with an ovary-derived cRNA probe in serial sections of fetal, fetoneonatal, and adult male rat brains and then performed steroidal manipulations to evaluate the sex-steroidal effects on AromP450 in adult orchiectomized and adrenalectomized (OCX + ADX) male rats. As a result, prominent mRNA signals were detected in the fetal (i.e., the anterior medial preoptic nucleus) and fetoneonatal (i.e., the medial preopticoamygdaloid neuronal arc) groups, although no detectable signal was found in the "young-to-adult" group (i.e., the central amygdaloid nucleus). In addition, the "fetoneonatal" AromP450-I neurons were prominently reduced in number and intensity after OCX + ADX and then were reinstated by the administration of dihydrotestosterone, testosterone, or 17beta-estradiol. In contrast, none of the sex steroids had any significant effects on the young-to-adult group. Several possible explanations were explored for why the young-to-adult group may differ in aromatase expression and regulation, including the possibility that distinct splicing variants or isozymes for aromatase exist in the rat brain.

Neurochemical Characterization and Sexual Dimorphism of Projections from the Brain to Abdominal and Subcutaneous White Adipose Tissue in the Rat

“…Testosterone is converted to estrogen in males via the aromatase enzyme, which is expressed in many tissues including adipose tissue and brain (Harada et al, 1993). This enzyme is regionally expressed in brain regions such as the medial preoptic area and estrogen acts locally (Zhao et al, 2007). Regardless of the underlying mechanisms that come into play, the preferential association of ER␣ with neurons projecting multisynaptically to rWAT is consistent with the observation that introduction of exogenous estrogen into the CNS dramatically reduces rWAT in males (Clegg et al, 2006).…”

Early regulation of brain aromatase (cyp19a1b) by estrogen receptors during zebrafish development

“…The fact that an esr1 signal was observed at these stages in the liver suggests that the riboprobe used is correct. This is further suggested by the fact that the liver esr1 signal overlaps prox1 mRNA (data not shown) an early marker of embryonic liver in zebrafish (Zhao et al, 2007). Expression of esr1 in the liver is likely related to the fact that this organ is an important target tissue for E2 in all oviparous species (Pakdel et al, 1991;Flouriot et al, 1996).…”

Neonatal testosterone suppresses a neuroendocrine pulse generator required for reproduction

“…The anatomical targets of T thus express both aromatase and ERa, which are two combined features of the neonatal periventricular area (PeV) 23 . In the neonatal PeV, ERa-positive cells are all neurons (Figs 5a and 6a); indeed, removing the PeV from hypothalamic slices harvested at P5, while without any effect on VP neurons, abolished the bursting activity of the OT neurons in the cultures of both sexes, that is, replicated the effect of T (Fig.…”