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Region-specific testosterone modulation of
the vasotocin-immunoreactive system in male dark-eyed junco, Junco hyemalis.
Plumari L, Plateroti S, Deviche P, Panzica GC.
Rita Levi Montalcini Center for Brain Repair, Department of Anatomy, Pharmacology
and Forensic Medicine, Laboratory of Neuroendocrinology, University of Torino,
Corso M. D'Azeglio 52, I-10126 Turin, Italy.
The nonapeptide vasotocin (VT) is the avian equivalent of the mammalian antidiuretic
hormone vasopressin and is believed to control aggressive and reproductive
behaviors. Brain VT distribution has been described in several domesticated
avian species. We previously demonstrated that VT distribution in the brain
of a free-ranging male passerine, the dark-eyed Junco, Junco hyemalis, resembles
that in domesticated birds. A preliminary study also suggested that the VT-immunoreactive
(VT-ir) system of juncos is regulated by testosterone (T), as is the case
of galliforms. To test this hypothesis, we investigated the effects of castration
and T replacement on brain VT-ir innervation in adult male juncos. Castration
reduced VT-ir innervation in the lateral septum (SL), the medial preoptic
nucleus, the nucleus of the stria terminalis and the intercollicularis nucleus.
These effects of castration were largely reversed by T treatment at high
physiological doses, but significantly so only for the SL. Given the demonstrated
behavioral role of the above VT-ir-containing brain regions, the results
suggest that these regions may be sites of action of VT on reproductive behaviors.
PMID: 14746916 [PubMed - indexed for MEDLINE]
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Changes in the arginine-vasopressin immunoreactive
systems in male mice lacking a functional aromatase gene.
Plumari L, Viglietti-Panzica C, Allieri F, Honda S, Harada
N, Absil P, Balthazart J, Panzica GC.
Laboratory of Neuroendocrinology, Rita Levi Montalcini Centre for Brain Repair,
Department of Anatomy, Pharmacology and Forensic Medicine, University of
Torino, Torino, Italy.
In male rodents, the arginine-vasopressin-immunoreactive (AVP-ir) neurones
of the bed nucleus of the stria terminalis (BNST) and medial amygdala are
controlled by plasma testosterone levels (decreased after castration and
restored by exogenous testosterone). AVP transcription in these nuclei is
increased in adulthood by a synergistic action of the androgenic and oestrogenic
metabolites of testosterone and, accordingly, androgen and oestrogen receptors
are present in both BNST and medial amygdala. We used knockout mice lacking
a functional aromatase enzyme (ArKO) to investigate the effects of a chronic
depletion of oestrogens on the sexually dimorphic AVP system. Wild-type (WT)
and ArKO male mice were perfused 48 h after an i.c.v. colchicine injection
and brain sections were then processed for AVP immunocytochemistry. A prominent
decrease (but not a complete suppression) of AVP-ir structures was observed
in the BNST and medial amygdala of ArKO mice by comparison with the WT. Similarly,
AVP-ir fibres were reduced in the lateral septum of ArKO mice and but not
in the medial preoptic area, a region where the AVP system is not sexually
dimorphic in rats. No change was detected in the supraoptic and suprachiasmatic
nuclei. However, a decrease in AVP-ir cell numbers was however, detected
in one subregion of the paraventricular nucleus. These data support the hypothesis
that the steroid-sensitive sexually dimorphic AVP system of the mouse forebrain
is mainly under the control of aromatized metabolites of testosterone.
PMID: 12472878 [PubMed - indexed for MEDLINE]
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Estradiol mediates effects of testosterone
on vasotocin immunoreactivity in the adult quail brain.
Viglietti-Panzica C, Balthazart J, Plumari L, Fratesi S, Absil
P, Panzica GC.
Department of Anatomy, Pharmacology, and Forensic Medicine, Laboratory of
Neuroendocrinology, Rita Levi Montalcini Center for Brain Repair, University
of Torino, c.so M. D'Azeglio 52, Torino, I-10126, Italy.
In adult male quail, the activation of sexual behavior by testosterone (T)
is mediated at the cellular level by the interaction of T metabolites with
intracellular steroid receptors. In particular, the aromatization of T into
an estrogen plays a key limiting role. Nonaromatizable androgens such 5alpha-dihydrotestosterone
(DHT) synergize with estradiol (E2) to activate the behavior. Given that
the density of vasotocin (VT) immunoreactive structures is increased by T
in adult male quail and that VT injections affect male behavior, we wondered
whether the expression of VT is also affected by T metabolites such as E2
and DHT. We analyzed here, in castrated male quail, the effects of a treatment
with T, E2, DHT, or E2 + DHT on sexual behavior and brain VT immunoreactivity.
The restoration by T of the VT immunoreactivity in the medial preoptic nucleus,
bed nucleus striae terminalis, and lateral septum of castrated male quail
could be fully mimicked by a treatment with E2. The androgen DHT had absolutely
no effect on the VT immunoreactivity in these conditions and, at the doses
used here, DHT did not synergize with E2 to enhance the density of VT immunoreactive
structures. These effects of T metabolites in the brain were not fully correlated
with their effects on the activation of male copulatory behavior, suggesting
that the increase in VT expression in the brain does not represent a necessary
step for the activation of behavior. Although VT expression in the medial
preoptic nucleus and bed nucleus striae terminalis is often tightly correlated
with the expression of male copulatory behavior, VT presumably does not represent
simply one step in the biochemical cascade of events that is induced by T
in the brain and leads to the expression of male sexual behavior.
PMID: 11716574 [PubMed - indexed for MEDLINE]
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Central vasotocin-immunoreactive system in
a male passerine bird (Junco hyemalis).
Panzica GC, Plumari L, Garcia-Ojeda E, Deviche P.
Department of Anatomy, Pharmacology, and Forensic Medicine, University of
Torino, Italy. giancarlo.panzica@unito.it
Previous investigations have identified regions of the avian brain that contain
immunoreactive vasotocinergic (VT-ir) cell bodies and fibers. These studies
exclusively used domesticated species, and the relevance of the findings
for free-living birds has not been established. The present study used immunocytochemistry
to determine the neuroanatomical distribution of the VT-ir system in the
brain of a well-studied male passerine bird (dark-eyed junco, Junco hyemalis)
obtained from a natural population in interior Alaska (65 degrees N, 147
degrees W). VT-ir cell bodies were observed in several brain regions (paraventricular
and supraoptic nuclei, nucleus of the stria terminalis), where they have
been described in other oscine species. VT-ir fibers were widespread in many
brain regions and were especially abundant in the medial preoptic nucleus,
the basal region of the septum, and the hypothalamic-neurohypophyseal tract.
Fibers were also present in brain regions that are involved in the control
of vocal behavior including the ventromedial capsular region of the nucleus
robustus archistriatalis and the dorsomedial portion of the mesencephalic
nucleus intercollicularis. The widespread brain distribution of VT-ir cell
bodies and fibers in juncos generally resembles that of domestic birds and
suggests a role for this neuropeptide in the control of reproductive behavior
and physiology.
PMID: 10363714 [PubMed - indexed for MEDLINE]
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