The distribution of the coactivator SRC-1 is sexually differentiated in the song control nuclei of male and female canaries

Poster (2003)

Sex differences in the distribution of the steroid receptor coactivator SRC-1 in the song control nuclei of male and female canaries.

in Brain Research (2003), 959(2), 263-74

The steroid receptor coactivator SRC-1 modulates ligand-dependent transactivation of several nuclear receptors, including the receptors for sex steroid hormones. The distribution of SRC-1 transcripts was ... [more ▼]

The steroid receptor coactivator SRC-1 modulates ligand-dependent transactivation of several nuclear receptors, including the receptors for sex steroid hormones. The distribution of SRC-1 transcripts was analyzed here by in situ hybridization in coronal sections through the brain of male and female canaries. A broad but heterogeneous distribution of SRC-1 transcripts was observed with high numbers of densely labeled cells being present in many steroid-sensitive areas including the medial preoptic nucleus, several hypothalamic nuclei, five song control nuclei (HVc, the lateral and medial portion of the magnocellular nucleus of the anterior neostriatum, area X and the nucleus uvaeformis) and several catecholaminergic areas (area ventralis of Tsai, substantia nigra, locus coeruleus). The volume of two song control nuclei, HVc and area X were reconstructed based on the boundaries of the cell groups exhibiting a denser SRC-1 expression as compared to the surrounding areas. Sex differences in the expression of SRC-1 were also detected in several song control nuclei. In particular, the volume of HVc based on the high density of SRC-1 expression was significantly larger in males than in females. The effect of steroids on the song control system could be, at least in part, indirect and result from a modulation by steroids of the catecholaminergic inputs to the song control nuclei. The presence of the steroid receptor coactivator SRC-1 in the telencephalic song control nuclei and in the catecholaminergic cell groups that innervate the song system supports the idea that SRC-1 expression could play an active role in the control of singing behavior by modulating estrogen and androgen receptor action at both locations. [less ▲]

Song activation by testosterone is associated with an increased catecholaminergic innervation of the song control system in female canaries

in Neuroscience (2003), 121(3), 801-814

In canaries, singing and a large number of morphological features of the neural system that mediates the learning, perception and production of song exhibit marked sex differences. Although these ... [more ▼]

In canaries, singing and a large number of morphological features of the neural system that mediates the learning, perception and production of song exhibit marked sex differences. Although these differences have been mainly attributed to sex-specific patterns of the action of testosterone and its metabolites, the mechanisms by which sex steroids regulate brain and behavior are far from being completely understood. Given that the density of immunoreactive catecholaminergic fibers that innervate telencephalic song nuclei in canaries is higher in males, which sing, than in females, which usually do not sing, we hypothesized that some of the effects induced by testosterone on song behavior are mediated through the action of the steroid on the catecholaminergic neurons which innervate the song control nuclei. Therefore, we investigated in female canaries the effects of a treatment with exogenous testosterone on song production, on the volume of song control nuclei, and on the catecholaminergic innervation of these nuclei as assessed by immunocytochemical visualization of tyrosine hydroxylase. Testosterone induced male-like singing in all females and increased by about 80% the volume of two telencephalic song control nuclei, the high vocal center (HVC) and the nucleus robustus archistriatalis (RA). Testosterone also significantly increased the fractional area covered by tyrosine hydroxylase-immunoreactive structures (fibers and varicosities) in most telencephalic song control nuclei (HVC, the lateral and medial parts of the magnocellular nucleus of the anterior neostriatum, the nucleus interfacialis, and to a lesser extent RA). By contrast, testosterone did not affect the catecholaminergic innervation of the telencephalic areas adjacent to HVC and RA. Together these data demonstrate that, in parallel to its effects on song behavior and on the morphology of the song control system, testosterone also regulates the catecholaminergic innervation of most telencephalic song control nuclei in canaries. The endocrine regulation of singing may thus involve the neuromodulatory action of specialized dopaminergic and/or noradrenergic projections onto several key parts of the song control system. (C) 2003 IBRO. Published by Elsevier Ltd. All rights reserved. [less ▲]

The neuroendocrinology of reproductive behavior in Japanese quail

in Domestic Animal Endocrinology (2003), 25

Sex steroid hormones such as testosterone have widespread effects on brain physiology and function but one of their best characterized effects arguably involves the activation of male sexual behavior ... [more ▼]

Sex steroid hormones such as testosterone have widespread effects on brain physiology and function but one of their best characterized effects arguably involves the activation of male sexual behavior. During the past 20 years we have investigated the testosterone control of male sexual behavior in an avian species, the Japanese quail (Coturnix japonica).We briefly reviewhere the main features and advantages of this species relating to the investigation of fundamental questions in the field of behavioral neuroendocrinology, a field that studies inter-relationship among hormones, brain and behavior. Special attention is given to the intracellular metabolism of testosterone, in particular its aromatization into an estrogen, which plays a critical limiting role in the mediation of the behavioral effects of testosterone. Brain aromatase activity is controlled by steroids which increase the transcription of the enzyme, but afferent inputs that affect the intraneuronal concentrations of calcium also appear to have a pronounced effect on the enzyme activity through rapid changes in its phosphorylation status. The physiological significance of these slowgenomic and rapid, presumably non-genomic, changes in brain aromatase activity are also briefly discussed. [less ▲]

Dopamine activates noradrenergic receptors in the preoptic area

in Journal of Neuroscience (2002), 22(21), 9320-9330

Dopamine (DA) facilitates male sexual behavior and modulates aromatase activity in the quail preoptic area (POA). Aromatase neurons in the POA receive dopaminergic inputs, but the anatomical substrate ... [more ▼]

Dopamine (DA) facilitates male sexual behavior and modulates aromatase activity in the quail preoptic area (POA). Aromatase neurons in the POA receive dopaminergic inputs, but the anatomical substrate that mediates the behavioral and endocrine effects of DA is poorly understood. Intracellular recordings showed that 100 muM DA hyperpolarizes most neurons in the medial preoptic nucleus (80%) by a direct effect, but depolarizes a few others (10%). DA-induced hyperpolarizations were not blocked by D1 or D2 antagonists (SCH-23390 and sulpiride). Extracellular recordings confirmed that DA inhibits the firing of most cells (52%) but excites a few others (24%). These effects also were not affected by DA antagonists (SCH-23390 and sulpiride) but were blocked by alpha(2)-(yohimbine) and alpha(1)-(prazosin) noradrenergic receptor antagonists, respectively. Two dopamine-beta-hydroxylase (DBH) inhibitors (cysteine and fusaric acid) did not block the DA-induced effects, indicating that DA is not converted into norepinephrine (NE) to produce its effects. The pK(B) of yohimbine for the receptor involved in the DA- and NE-induced inhibitions was similar, indicating that the two monoamines interact with the same receptor. Together, these results demonstrate that the effects of DA in the POA are mediated mostly by the activation of alpha(2) (inhibition) and alpha(1) (excitation) adrenoreceptors. This may explain why DA affects the expression of male sexual behavior through its action in the POA, which contains high densities of alpha(2)-noradrenergic but limited amounts of DA receptors. This study thus clearly demonstrates the existence of a cross talk within CNS catecholaminergic systems between a neurotransmitter and heterologous receptors. [less ▲]

Context-dependent effects of castration and testosterone treatment on song in male European starlings

in Hormones & Behavior (2002), 42(3), 307-318

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as ... [more ▼]

Most seasonally breeding songbirds display dramatic seasonal fluctuations in plasma testosterone (T) levels and mate attraction behaviors, including song. However, males of some songbird species, such as the European starling (Stumus vulgaris), continue to sing at high levels after the breeding season, when T levels are basal. In male starlings song during the breeding season functions mainly to attract mates, whereas song during the nonbreeding season appears unrelated to reproduction. This suggests that song produced in a context unrelated to female courtship, unlike song directed toward females, is not regulated by plasma T. In captive males housed in large outdoor aviaries we explored the relationship between plasma T and song produced during the breeding season within and outside a courtship context. This was achieved by determining the effects of castration and subsequent T treatment on song and mate attraction behaviors in both the presence and the absence of a female. Compared to intact males, castrated males did not show reduced song activity in the absence of a female for at least 6 months after the operation, strongly suggesting that the expression of noncourtship song is not regulated by plasma T. Likewise, we found that experimentally elevating T levels in castrated males did not affect noncourtship song rates. However, control castrated males receiving empty implants tended to show reduced noncourtship song rates after implantation. This may have been due to a suppressive effect caused by the presence of the T-implanted castrated males in the same aviary. In contrast, courtship singing was clearly controlled by plasma T: it was abolished by castration and restored by subsequent T replacement when males were housed both individually and in a group situation. High plasma levels of T also appeared necessary for the activation of three other behavioral traits critical for mate attraction, namely, nesthole occupancy, spending time (singing) in a nesthole, and carrying green nesting material into a nesthole. (C) 2002 Elsevier Science (USA). [less ▲]

Sexual partner preference requires a functional aromatase (Cyp19) gene in male mice

in Hormones & Behavior (2002), 42(2), 158-171

Sexual motivation, sexual partner preference, and sexual performance represent three different aspects of sexual behavior that are critical in determining the reproductive success of a species. Although ... [more ▼]

Sexual motivation, sexual partner preference, and sexual performance represent three different aspects of sexual behavior that are critical in determining the reproductive success of a species. Although the display of sexual behavior is under strict hormonal control in both sexes, the relative roles of androgen and estrogen receptors in activating the various components of male sexual behavior are still largely unknown. A recently developed mouse model that is deficient in estradiol due to targeted disruption of exons 1 and 2 of the Cyp19 gene (aromatase knockout (ArKO) mice) was used here to analyze the role of estradiol in the control of all three aspects of male sexual behavior. When tested in a Y-maze providing volatile olfactory cues, male ArKO mice did not show a preference for the odors from an estrous female over those from an intact male, whereas wildtype (WT) and heterozygous (HET) males clearly preferred to sniff estrous odors. When provided with visual and olfactory cues, male ArKO mice also failed to show a preference for an estrous female when given a choice between an estrous female and an empty arm. However, sexual partner preferences of male ArKO mice were not sex-reversed: they did not prefer to investigate an intact male over an estrous female or empty arm. Thus, male ArKO mice seemed to have general deficits in discriminating between conspecifics by using olfactory and visual cues. Male coital behavior was also severely impaired in male ArKO mice: they displayed significantly fewer mounts, intromissions, and ejaculations than WT and HET males. Latencies to first mount or intromission were also significantly longer in ArKO males compared to WT and HET males, in addition to them showing less interest in investigating olfactory and visual cues in a Y-maze, suggesting that they were sexually less motivated. However, three out of seven male ArKO mice were capable of siring litters provided they were housed with a female for a prolonged period of time. In conclusion, aromatization of testosterone to estradiol appears to be essential for sexual motivation and sexual partner preference. By contrast, estradiol may play only a limited role in the expression of male coital behaviors. (C) 2002 Elsevier Science (USA). [less ▲]

The parvocellular vasotocin system of Japanese quail: A developmental and adult model for the study of influences of gonadal hormones on sexually differentiated and behaviorally relevant neural circuits

in Environmental Health Perspectives (2002), 110(Suppl. 3), 423-428

Vasotocin (VT; the antidiuretic hormone of birds) is synthesized by diencephalic magnocellular neurons projecting to the neurohypophysis. A sexually dimorphic system of VT-immunoreactive (ir ... [more ▼]

Vasotocin (VT; the antidiuretic hormone of birds) is synthesized by diencephalic magnocellular neurons projecting to the neurohypophysis. A sexually dimorphic system of VT-immunoreactive (ir) parvocellular elements has been described within the male medial preoptic nucleus (POM) and the nucleus of the stria terminalis, pars medialis (BSTm). VT-ir fibers are present in many diencephalic and extradiencephalic locations, and quantitative morphometric analyses demonstrated their sexually dimorphic distribution in regions involved in the control of different aspects of reproduction. Moreover, systemic or intracerebroventricular injections of VT markedly inhibit the expression of some aspects of male sexual behavior. In adult animals, circulating levels of testosterone (T) have a profound influence on the VT immunoreactivity within BSTm, POM, and lateral septum. Castration markedly decreases the immunoreaction, whereas T-replacement therapy restores a situation similar to the intact birds. We observed no changes in gonadectomized females treated with T. These changes parallel similar changes in male copulatory behavior (not present in castrated male quail, fully expressed in castrated, T-treated males). The restoration by T of the VT immunoreactivity in castrated male quail could be fully mimicked by a treatment with estradiol (E-2), suggesting that the aromatization of T into E-2 may play a key limiting role in both the activation of male sexual behavior and the induction of VT synthesis. This dimorphism has an organizational nature: administration of E-2 to quail embryos (a treatment that abolishes male sexual behavior) results in a dramatic decrease of the VT immuno reactivity in sexually dimorphic regions. Conversely, the inhibition of E-2 synthesis during embryonic life (a treatment that stimulates the expression of male copulatory behavior in treated females exposed in adulthood to T) results in a malelike distribution of VT immunoreactivity. The VT parvocellular system of the Japanese quail can therefore be considered an accurate marker of the sexual differentiation of brain circuits mediating copulatory behavior and could be a very sensitive indicator of the activity of estrogenlike substances on neural circuits. [less ▲]

The assessment of nociceptive and non-nociceptive skin sensitivity in the Japanese quail (Coturnix japonica)

in Journal of Neuroscience Methods (2002), 116(2), 135-146

We evaluated the efficacy of two nociceptive tests, the hot water (HWT) and the foot pressure tests (FPT), and one non-nociceptive test (Semmes-Weinstein test, SWT) in assessing skin sensitivity in ... [more ▼]

We evaluated the efficacy of two nociceptive tests, the hot water (HWT) and the foot pressure tests (FPT), and one non-nociceptive test (Semmes-Weinstein test, SWT) in assessing skin sensitivity in conscious Japanese quail. All stimuli elicited a reflex-like, strongly reproducible response. Responses in the HWT and FPT were identified as typical nocifensive flight-fight behavior. In untreated birds, these responses occurred at temperatures and forces described previously as noxious. In the SWT, two responses were observed: a slight ruffling of the cloacal gland feathers due to the stimulation of the cloacal gland, and a brief extension of the limbs due to the stimulation of the ilium or pectoral apterium. These reactions occurred at intensities recognized as innocuous. Morphine significantly altered the response latency and threshold in the HWT and FPT, but had no effect in the SWT. However, the SWT response threshold was significantly increased by local application of xylocaine. Taken together, the pattern of the responses, the intensities and the effects of morphine and xylocaine allowed to distinguish between nociceptive and non-nociceptive tests. They also demonstrate the efficacy of these tests to evaluate skin sensitivity in quail and to assess its modulation by chemical factors that affect somatosensory processes. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

The origin of catecholaminergic inputs to the song control nucleus RA in canaries

in Neuroreport (2002), 13(5), 649-653

Song control nuclei in oscines receive dense catecholaminergic inputs but their anatomical origin is poorly understood. We analyzed catecholaminergic inputs to the nucleus robustus archistriatalis (RA) in ... [more ▼]

Song control nuclei in oscines receive dense catecholaminergic inputs but their anatomical origin is poorly understood. We analyzed catecholaminergic inputs to the nucleus robustus archistriatalis (RA) in canaries by retrograde tract-tracing combined with immunocytochemistry for tyrosine hydroxylase. In both sexes, dopaminergic inputs to RA come mostly from the A1 1 (mesencephalic central gray) and A10 (area ventralis of Tsai) cell groups but the locus coeruleus and subcoeruleus (A6) also send noradrenergic projections to RA. No input originates in the hypothalamic and in the A5 to A1 catecholaminergic groups. These findings and previous work on the high vocal center (HVc) indicate that the two major nuclei of the motor pathway controlling song production (RA and HVc) receive catecholaminergic inputs of similar origins. [less ▲]