Brain Research 879 2000 174–182 www.elsevier.com locate bres
Research report
Androgen receptor-immunoreactivity in the forebrain of the Eastern Fence lizard Sceloporus undulatus
a , b
a b
M.M. Moga , B.M. Geib , D. Zhou , G.S. Prins
a
Terre Haute Center for Medical Education , Indiana University School of Medicine, Terre Haute, IN 47809, USA
b
Department of Urology , University of Illinois at Chicago, Chicago, IL 60612, USA
Accepted 25 July 2000
Abstract
Androgen receptor AR distribution in the lizard forebrain and optic tectum was examined using PG21 immunohistochemistry. In the male Eastern Fence lizard, AR-immunoreactive -ir nuclei were observed in the medial preoptic area, ventromedial and arcuate
hypothalamic nuclei, periventricular hypothalamus, premammillary nucleus, bed nucleus of the stria terminalis, and ventral posterior amygdala. Punctate immunostaining of neuronal processes axons and or dendrites was concentrated in the cortex, hypothalamus, and
optic tectum. AR-ir nuclei in the female brain were confined to the ventral posterior amygdala and ventromedial hypothalamic nucleus. The AR distribution in the lizard brain is similar to that reported for other vertebrate classes. Sex differences in AR-immunoreactivity may
contribute to sex-specific behaviors in the Eastern Fence lizard.
2000 Elsevier Science B.V. All rights reserved.
Theme : Other systems of the CNS
Topic : Comparative neuroanatomy
Keywords : Steroid receptor; Hypothalamus; Amygdala; Cortex; Reptile
1. Introduction species-specific AR-ir cell clusters, such as the song
control nuclei of songbirds [1,2], and have increased our Male reproductive behavior is activated by circulating
understanding of the neural basis of reproductive behaviors sex steroids, particularly the androgens testosterone and
[20]. 5a-dihydrotestosterone DHT. Androgens elicit sex-spe-
To date, there has been no immunocytochemical study cific behaviors by acting directly on androgen receptors in
of AR in the reptilian brain. An early study by Morrell et
3
the brain or through indirect activation of brain estrogen al. [26] employed
H-testosterone autoradiography to receptors via androgen aromatization [32]. In whiptail and
identify androgen-concentrating cells in the lizard brain. anole lizards, androgens are more effective than estrogenic
Some of the androgen-concentrating cells which they metabolites in eliciting male sexual behavior [14,38,42].
identified may actually have been estrogen-concentrating The distribution of androgen receptor AR protein and
cells, as circulating testosterone is aromatized to estrogen mRNA in the brain shows a similar pattern among the
in certain areas of the brain. Recently, Young et al. [46] different vertebrate classes, including bird [2,36], fish [19],
analyzed the distribution of AR mRNA in the brain of the reptile [46], and mammal [21,35]. In each of these classes,
whiptail lizard using in situ hybridization. Although highly AR-positive cells are concentrated in the hypothalamus
sensitive, this method cannot distinguish between cyto- and amygdala, specifically in brain nuclei that have been
plasmic and nuclear staining, or identify AR-positive implicated in male reproductive and aggressive behavior.
dendrites and axons. In the present study, we map the Comparative studies have proven useful in delineating
distribution of AR in the forebrain of the Eastern Fence lizard Sceloporus undulatus using immunocytochemistry.
The AR antibody employed in the present experiments
Corresponding author. Tel.: 11-812-237-3420; fax: 11-812-237-
PG21 is directed against amino acids 1–21 of the rat AR
7646. E-mail address
: mefmogathcme.indstate.edu M.M. Moga.
[30]. The lizard AR shows a high degree of sequence
0006-8993 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 0 0 6 - 8 9 9 3 0 0 0 2 7 7 1 - 2
M .M. Moga et al. Brain Research 879 2000 174 –182
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homology with ARs in other species [47]. The DNA- Elite Standard ABC kit; Vector for 1–2 h. After several
binding and C-terminal ligand-binding domains of AR are rinses in PBS, the sections were reacted in a solution of
the most highly conserved [37]. However, positions 1–35 0.05 3,39-diaminobenzidine tetrahydrochloride DAB;
and 230–268 in the AR are far less variant than the rest of Sigma-0.025 nickel chloride-0.01 H O in 0.1 M Tris
2 2
the N-terminal domain [37]. A low degree of variance in buffer, pH 7.4, for 10 min. The sections were mounted on
amino acids 1–21 of the AR may explain the ability of the gel-coated slides, dehydrated through alcohols and xylene,
PG21 antibody to label ARs in diverse tissue types in a and coverslipped with Permount Fisher.
variety of vertebrates, including mammal [11,13,18,21, The specificity of the PG21 antibody was tested by, 1
44,45,49], fish [15], bird [2,36], and amphibian [16]. preabsorption of the primary antibody with its respective
peptide AR21; amino acids 1–21 of the rat AR, 2 preabsorption of the primary antibody with a peptide
2. Methods derived from a different portion of the rat AR AR462;
