Brain Aromatization and Its Associated Structures.

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

“…However, there seems still to be some confusion, because some groups, using different antibodies, against a 20-amino-acid oligopeptide (379 -398) of rat AromP450 (Sanghera et al, 1991) and against a unique form of human placental AromP450 antigen (51 kDa; Balthazart et al, 1991a;Jakab et al, 1993), have reported that there is no or only a slight AromP450 expression in the medial preoptic or amygdaloid region. Although such a discrepancy is considered to be attributable to different recognition sites or cross-reactions among those antisera (see Shinoda, 1994a), the current IHC and ISH histochemical results in serial sections have definitively shown that the major aromatizing neurons are localized to the mPOAM in terms of their prominent immunoreactivity, hybridization signals, and cell numbers. Previous radioisotope-labeled ISH studies (although they might be less appropriate for detailed histochemical analyses than nonradioisotopelabeled ISH ones) have also shown the localization of the major AromP450 mRNA expression in the mPOAM of mammalian brains (Lauber and Lichtensteiger, 1994;Morell, 1996, 1997;Lauber et al, 1997;Roselli et al, 1998Roselli et al, , 2001).…”

“…The brain has been clarified as one of the major tissues with a prominent androgen-to-estrogen-biosynthesizing potential by brain aromatase through fetal to adult stages, particularly in males (Naftolin et al, 1971(Naftolin et al, , 1975McEwen et al, 1977;MacLusky and Naftolin, 1981;George and Ojeda, 1982;Roselli, et al, 1985Roselli, et al, , 1998Roselli, et al, , 2001Shinoda, 1994aShinoda, , 1998Lauber and Lichtensteiger, 1994). Early immunohistochemical results in mammalian brains (Shinoda et al, 1989;Balthazart et al, 1991a;Sanghera et al, 1991;Jakab et al, 1993) were, however, inconsistent with previously accumulated biochemical data in terms of their forebrain distribution (Naftolin et al, 1971(Naftolin et al, , 1972(Naftolin et al, , 1975Weisz and Gibbs, 1974;Selmanoff et al, 1977;George and Ojeda, 1982;Roselli et al, 1985); neurons in the medial preoptic and medial amygdaloid regions, where the aromatase activity is high, were reported to be basically de-void of the aromatase-P450 (AromP450) immunoreactivity.…”

“…Early immunohistochemical results in mammalian brains (Shinoda et al, 1989;Balthazart et al, 1991a;Sanghera et al, 1991;Jakab et al, 1993) were, however, inconsistent with previously accumulated biochemical data in terms of their forebrain distribution (Naftolin et al, 1971(Naftolin et al, , 1972(Naftolin et al, , 1975Weisz and Gibbs, 1974;Selmanoff et al, 1977;George and Ojeda, 1982;Roselli et al, 1985); neurons in the medial preoptic and medial amygdaloid regions, where the aromatase activity is high, were reported to be basically de-void of the aromatase-P450 (AromP450) immunoreactivity. The discrepancy might be due to the inappropriate antigen quality of the synthesized fragments (oligopeptide) or purified AromP450 or the antibody specificity in aldehyde-fixed brain tissues (for review see Shinoda, 1994a). With a highly monospecific AromP450 antibody Kitawaki et al, 1989), reliable immunohistochemical localization of mammalian brain aromatase, which accords with the biochemical distribution, was first successfully clarified in neurons of the medial amygdaloid and preoptic/hypothalamic regions and some limbic structures during developing (Shinoda et al, 1994) and adult (Shinoda, 1994b) stages of the rat brain.…”

“…The young-to-adult group occurs after postnatal day 14 in the lateral division of the central amygdaloid nucleus (lCeAm), oval nucleus of the bed nucleus of the stria terminalis (ovBST), and lateral septal nucleus (LS) and gradually increases to the moderate AromP450 immunoreactivity in the young-toadulthood group. The presence of three distinct groups with histochemically different characteristics suggests the possible occurrence of region-specific alternative splicing or existence of AromP450 isozymes in the brain (Shinoda, 1994a;Shinoda et al, 1994). Expressions of AromP450 protein and mRNA, however, have never been compared via IHC and ISH among the three groups.…”

Physiology of Reproduction

“…Defeminization of the brain is induced by estrogen, which is produced from testosterone locally by the brain aromatase, since defeminization of the brain is also induced by neonatal estrogen treatment but not by dihydrotestosterone (DHT), which is nonaromatizable testosterone. Aromatase has been found in various areas of the male rat brain (Shinoda, 1994). Localization of estrogen receptors and aromatase correlate well (Kawata, 1995;Hayashi, S. et al, 1997).…”