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The Bengalese finch was domesticated more than 250 years ago from the wild white-rumped munia (WRM). Similar to other domesticated species, Bengalese finches show a reduced fear response and have lower corticosterone levels, compared to WRMs. Bengalese finches and munias also have different song types. Since oxytocin (OT) has been found to be involved in stress coping and auditory processing, we tested whether the OT sequence and brain expression pattern and content differ in wild munias and domesticated Bengalese finches. We sequenced the OT from 10 wild munias and 11 Bengalese finches and identified intra-strain variability in both the untranslated and protein-coding regions of the sequence, with all the latter giving rise to synonymous mutations. Several of these changes fall in specific transcription factor-binding sites, and show either a conserved or a relaxed evolutionary trend in the avian lineage, and in vertebrates in general. Although in situ hybridization in several hypothalamic nuclei did not reveal significant differences in the number of cells expressing OT between the two strains, real-time quantitative PCR showed a significantly higher OT mRNA expression in the cerebrum of the Bengalese finches relative to munias, but a significantly lower expression in their diencephalon. Our study thus points to a brain region-specific pattern of neurochemical expression in domesticated and wild avian strains, which could be linked to domestication and the behavioral changes associated with it.

The Bengalese finch was domesticated more than 250 years ago from the wild white-rumped munia. Similar to other domesticated species, Bengalese finches show a reduced fear response and have lower corticosterone levels, compared to white-rumped munias. Bengalese finches and munias also have different song types. Since oxytocin (OT) has been found to be involved in stress coping and auditory processing, we tested whether the OT sequence and brain expression pattern and content differ in wild munias and domesticated Bengalese finches. We identified intra-strain variability in the untranslated regions of the OT sequence in Bengalese finches in comparison to the munia OT. Several of these changes fall in specific transcription factor binding sites, which show either a conserved or a relaxed evolutionary trend in the avian lineage, and in vertebrates in general. Although in situ hybridization in several hypothalamic nuclei did not reveal significant differences in the number of cells expressing OT between the two strains, real-time quantitative PCR showed significantly lower OT mRNA expression in the diencephalon of the Bengalese finches relative to munias. Our study thus points to a decreased OT synthesis in the domestic strain compared with the wild strain in birds. This is an opposite pattern from that found in some domesticated mammals, suggesting that different processes of OT function might have occurred in mammals and birds under domestication.

Vocal communication is important for reproductive success in birds. Conspecific vocalization of birds is processed in the auditory system from ear to higher-order auditory regions in the telencephalon, including the caudomedial nidopallium (NCM). Higher-order auditory regions are involved in the perception of vocal communication in songbirds and nonsongbirds. In a nonsongbird parrot, the NCM of females is involved in the perception of song complexity, which has been considered an intersexually selected trait. Social information is thought to converge on the hypothalamus and is then transduced into a reproductive endocrine response. In another nonsongbird dove, the information from the courtship call is relayed to the hypothalamic neuroendocrine cells through the auditory thalamic nucleus. Together, the existing studies suggest that auditory inputs to higher-order auditory regions and the hypothalamic-pituitary-gonadal (HPG) axis are important for nonsongbird reproduction. It remains unclear whether the HPG axis receives auditory information from higher-order auditory regions.

During mammalian fertilization, sperm is fused with the oocyte's membrane, triggering the resumption of meiosis from the metaphase II arrest, the extrusion of the second polar body, and the exocytosis of cortical granules; these events are collectively called 'oocyte activation.' In all species studied to date, the transient rise in the cytosolic level of calcium (in particular, the repeated calcium increases called 'calcium oscillations' in mammals) is required for these events. Researchers have focused on identifying the factor(s) that can induce calcium oscillations during fertilization. Sperm‐specific phospholipase C, i.e., PLC zeta (PLCζ), is a strong candidate of the factor(s), and several research groups using different species obtained evidence that PLCζ is a sperm factor that can induce calcium oscillations during fertilization. However, postacrosomal sheath Tryptophan‐Tryptophan (WW)—domain‐binding protein (PAWP) was recently shown to have a pivotal role in inducing calcium oscillations in some species. In this review, we focus on PLCζ and PAWP as sperm factors, and we discuss this controversy: Which of these two molecules survives as a sperm factor?

The social environment changes circulating hormone levels and expression of social behavior in animals. Social information is perceived by sensory systems, leading to cellular and molecular changes through neural processes. Peripheral reproductive hormone levels are regulated by activity in the hypothalamic-pituitary-gonadal (HPG) axis. Until the end of the last century, the neurochemical systems that convey social information to the HPG axis were not well understood. Gonadotropin-inhibitory hormone (GnIH) was the first hypothalamic neuropeptide shown to inhibit gonadotropin release, in 2000. GnIH is now regarded as a negative upstream regulator of the HPG axis, and it is becoming increasingly evident that it responds to social cues. In addition to controlling reproductive physiology, GnIH seems to modulate the reproductive behavior of animals. Here, we review studies investigating how GnIH neurons respond to social information and describe the mechanisms through which GnIH regulates social behavior.

Male Japanese quail produce high-frequency crow vocalizations to attract females during the breeding season. The nucleus of intercollicularis (ICo) is the midbrain vocal center in birds and electrical stimulation of the ICo produces calls that include crowing. Noradrenaline plays a significant role in sexual behavior but the contribution of noradrenaline in the control of courtship vocalizations in quail has not been well established. Using dose-dependent intracerebroventricular injection of clonidine, an α2-adrenergic receptor- specific agonist, crowing vocalization was immediately suppressed. At the same time as crow suppression by clonidine there was a reduction of immediate early gene, zenk mRNA, in the ICo; no zenk mRNA expression was detected in the dorsomedial division of the nucleus. Using histochemistry, we determined that the ICo receives noradrenergic innervation and expresses α2A-adrenergic receptor mRNA. Taken together, these data suggest that noradrenaline regulates courtship vocalization in quail, possibly via the alpha2A- adrenergic receptor expressed on ICo neurons.

Vasoactive intestinal peptide (VIP) treatment induced mRNA expression of Prolactin (PRL) in the chicken anterior pituitary gland. VIP responsive element (VRE) of the PRL promoter was identified in the various bird species. However, transcription factor, which binds to VRE, has not yet been identified. Prolactin regulatory element-binding protein (PREB) gene cloned as a candidate transcription factor binds to VRE. Increases of mRNA levels of PRL and PREB during embryogenesis were identified. However, whether VIP affects levels of PRL and PREB mRNA during embryogenesis remains unknown. The effects of VIP and forskolin on mRNA expression of PRL and PREB in the embryonic anterior pituitary gland were assessed. Furthermore, administration of VIP to laying hens was conducted to examine the relationship between VIP and PREB mRNA expression. At day 14 of the embryonic growth stage, VIP treatment did not affect mRNA levels of either PRL or PREB, whereas forskolin treatment induced the increase of these mRNA levels. At day 20, both VIP and forskolin induced an increase of PRL and PREB mRNA levels. The administration of VIP significantly increased mRNA levels of PRL and PREB in the anterior pituitary gland of White Leghorn and Nagoya. These results indicate that the effects of VIP on PRL and PREB mRNA expression levels of VIP receptor may in turn affect PRL and PREB mRNA levels in the chicken anterior pituitary gland.

Biased mating due to female preferences towards certain traits in males is a major mechanism driving sexual selection, and may constitute an important evolutionary force in organisms with sexual reproduction. In birds, although the role of male ornamentation, plumage coloration, genetic dissimilarity, and body size have on mate selection by females have been examined extensively, few studies have clarified exactly how these characteristics affect female mate preferences. Here, we show that testosterone (T)-dependent male attractiveness enhances female preference for males of a polygamous species, the Japanese quail. A significant positive correlation between female mating preference and circulating T in the male was observed. The cheek feathers of attractive males contained higher levels of melanin and were more brightly colored. The ability of females to distinguish attractive males from other males was negated when the light source was covered with a sharp cut filter (cutoff

Social interactions rapidly modulate circulating hormone levels and behavioral patterns in most male animals. In male birds, sexual interaction or visual exposure to a conspecific female usually causes an increase in the levels of peripheral reproductive hormones, such as gonadotropins and androgens. Although the perception of a female presence is processed in the brain and peripheral hormonal levels are regulated by the hypothalamus-pituitary-gonadal (HPG) axis, the specific neural circuitry and neurochemical systems that translate social signals into reproductive physiology in male birds were not well understood until 2008. Today, there is growing evidence that two neuropeptides localized in the hypothalamus, gonadotropin-releasing hormone and gonadotropin-inhibitory hormone, are responsive to social information. These two neuropeptides have thus begun to be regarded as modulators translating social stimuli into changes in the levels of peripheral reproductive hormones. Here, we review previous studies that investigated the male responses of the HPG axis to the mere presence of a female or to sexual interaction, and describe the neurochemical pathways linking visual perception of a potential mate to rapid peripheral hormonal changes via the brain-pituitary endocrine system in sexually mature male Japanese quail.

Social interactions rapidly modulate circulating hormone levels and behavioral patterns in most male animals. In male birds, sexual interaction or visual exposure to a conspecific female usually causes an increase in the levels of peripheral reproductive hormones, such as gonadotropins and androgens. Although the perception of a female presence is processed in the brain and peripheral hormonal levels are regulated by the hypothalamus-pituitary-gonadal (HPG) axis, the specific neural circuitry and neurochemical systems that translate social signals into reproductive physiology in male birds were not well understood until 2008. Today, there is growing evidence that two neuropeptides localized in the hypothalamus, gonadotropin-releasing hormone and gonadotropin-inhibitory hormone, are responsive to social information. These two neuropeptides have thus begun to be regarded as modulators translating social stimuli into changes in the levels of peripheral reproductive hormones. Here, we review previous studies that investigated the male responses of the HPG axis to the mere presence of a female or to sexual interaction, and describe the neurochemical pathways linking visual perception of a potential mate to rapid peripheral hormonal changes via the brain-pituitary endocrine system in sexually mature male Japanese quail.

Bird species with vocal learning possess a projection from the telencephalic nucleus to the nucleus nervi hypoglossi, pars tracheosyringealis (XIIts) in the medulla, where a final common pathway that controls the vocal organ, i.e., the synrinx, originates. The anatomical basis of this projection has not been well investigated in one species of songbird, the Bengalese finch ( Lonchura striata var. domestica ). The present study used anterograde and retrograde tracing experiments to examine and describe this projection in Bengalese finches. Following iontophoretic injections of biotinylated dextran amine into the telencephalic nucleus robustus arcopallialis (RA), we detected anterograde-labeled terminations in the XIIts. In addition, labeled terminals were seen in other vocal–respiratory-related nuclei, such as the dorsomedial nucleus of the nucleus intercollicularis, nucleus infraolivaris superior, nucleus of the rostral ventrolateral medulla, nucleus parambigualis, nucleus ambiguous, and nucleus retroambigualis. Furthermore, following injections into the XIIts, we detected retrograde-labeled cell bodies scattered throughout the ipsilateral RA. The present results revealed that the direct projections of the RA to the XIIts in male Bengalese finches are similar to those in other songbirds with vocal learning abilities.

Several neuropeptides with the C-terminal Arg-Phe-NH(2) (RFa) sequence have been identified in the hypothalamus of a variety of vertebrates. The present study was conducted to isolate novel RFa peptides from the zebra finch brain. Peptides were isolated by immunoaffinity purification using an antibody that recognises avian RFa peptides. The isolated peptide consisted of 25 amino acids with RFa at its C-terminus. The sequence was SGTLGNLAEEINGYNRRKGGFTFRFa. Alignment of the peptide with vertebrate 26RFa has revealed that the identified peptide is the zebra finch 26RFa. We also cloned the precursor cDNA encoding this peptide. Synteny analysis of the gene showed a high conservation of this gene among vertebrates. In addition, we cloned the cDNA encoding a putative 26RFa receptor, G protein-coupled receptor 103 (GPR103) in the zebra finch brain. GPR103 cDNA encoded a 432 amino acid protein that has seven transmembrane domains. In situ hybridisation analysis in the brain showed that the expression of 26RFa mRNA is confined to the anterior-medial hypothalamic area, ventromedial nucleus of the hypothalamus and the lateral hypothalamic area, the brain regions that are involved in the regulation of feeding behaviour, whereas GPR103 mRNA is distributed throughout the brain in addition to the hypothalamic nuclei. When administered centrally in free-feeding male zebra finches, 26RFa increased food intake 24 h after injection without body mass change. Diencephalic GPR103 mRNA expression was up-regulated by fasting for 10 h. Our data suggest that the hypothalamic 26RFa-its receptor system plays an important role in the central control of food intake and energy homeostasis in the zebra finch.

The discovery of two novel avian neurosteroids in the quail brain, 7alpha- and 7beta-hydroxypregnenolone is described. Intracerebroventricular administration of 7alpha-hydroxypregnenolone, but not 7beta-hydroxypregnenolone was found to stimulate locomotor activity of male quail when spontaneous nocturnal activity is low. Diurnal changes in locomotor activity in male quail were found to be correlated with a diurnal change in the concentration of diencephalic 7alpha-hydroxypregnenolone. This correlation was a not seen in female quail which have a lower amplitude diurnal rhythm of locomotor activity and lower daytime concentrations of diencephalic 7alpha-hydroxypregnenolone. Treatment of male quail with melatonin was found to depress the synthesis of 7alpha-hydroxypregnenolone in the diencephalon. This is a previously undescribed role for melatonin in the regulation of neurosteroid synthesis in the brain of any vertebrate. We therefore deduced in male quail, that the nocturnal depression in locomotory activity is a consequence of a depression in diencephalic 7alpha-hydroxypregnenolone resulting from the inhibitory action of the nocturnal increase in melatonin. This observation may be of widespread significance for the molecular control of rhythmic locomotor activity in all vertebrates.

Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotropin secretion and socio-sexual behaviours. Oestrogen (neuroestrogen) synthesized in the brain from androgen by aromatase regulates male socio-sexual behaviours. Here we show that GnIH directly activates aromatase and increases neuroestrogen synthesis in the preoptic area (POA) and inhibits socio-sexual behaviours of male quail. Aromatase activity and neuroestrogen concentration in the POA are low in the morning when the birds are active, but neuroestrogen synthesis gradually increases until the evening when the birds become inactive. Centrally administered GnIH in the morning increases neuroestrogen synthesis in the POA and decreases socio-sexual behaviours. Centrally administered 17β-oestradiol at higher doses also inhibits socio-sexual behaviours in the morning. These results suggest that GnIH inhibits male socio-sexual behaviours by increasing neuroestrogen synthesis beyond its optimum concentration for the expression of socio-sexual behaviours. This is the first demonstration of any hypothalamic neuropeptide that directly regulates neuroestrogen synthesis., The conversion of testosterone into oestrogen in the brain is implicated in male aggressive behaviour. Ubuka et al. show that gonadotropin-inhibitory hormone inhibits male aggression by increasing oestrogen synthesis in the brain beyond its optimum concentration for the expression of aggressive behaviour.

Gonadotropin-inhibitory hormone (GnIH) was first identified in Japanese quail to be an inhibitor of gonadotropin synthesis and release. GnIH peptides have since been identified in all vertebrates, and all share an LPXRFamide (X = L or Q) motif at their C-termini. The receptor for GnIH is the G protein-coupled receptor 147 (GPR147), which inhibits cAMP signaling. Cell bodies of GnIH neurons are located in the paraventricular nucleus (PVN) in birds and the dorsomedial hypothalamic area (DMH) in most mammals. GnIH neurons in the PVN or DMH project to the median eminence to control anterior pituitary function via GPR147 expressed in gonadotropes. Further, GnIH inhibits gonadotropin-releasing hormone (GnRH) -induced gonadotropin subunit gene transcription by inhibiting the adenylate cyclase/cAMP/PKA -dependent ERK pathway in an immortalized mouse gonadotrope cell line (LT2 cells). GnIH neurons also project to GnRH neurons that express GPR147 in the preoptic area (POA) in birds and mammals. Accordingly, GnIH can inhibit gonadotropin synthesis and release by decreasing the activity of GnRH neurons as well as by directly inhibiting pituitary gonadotrope activity. GnIH and GPR147 can thus centrally suppress testosterone secretion and spermatogenesis by acting in the hypothalamic-pituitary-gonadal axis. GnIH and GPR147 are also expressed in the testis of birds and mammals, possibly acting in an autocrine/paracrine manner to suppress testosterone secretion and spermatogenesis. GnIH expression is also regulated by melatonin, stress and social environment in birds and mammals. Accordingly, the GnIH-GPR147 system may play a role in transducing physical and social environmental information to regulate optimal testicular activity in birds and mammals. This review discusses central and direct inhibitory effects of GnIH and GPR147 on testosterone secretion and spermatogenesis in birds and mammals.

International audience; Several neuropeptides possessing the RFamide motif at their C-termini (designated RFamide peptides) have been characterized in the hypothalamus of a variety of vertebrates. Since the discovery of the 26-amino acid RFamide peptide (termed 26RFa) from the frog brain, 26RFa has been shown to exert orexigenic activity in mammals and to be a ligand of the previously identified orphan G protein-coupled receptor GPR103. Recently, we have identified 26RFa in the avian brain by molecular cloning of the cDNA encoding the 26RFa precursor and mass spectrometry analysis of the mature peptide. 26RFa-producing neurons are exclusively located in the hypothalamus whereas GPR103 is widely distributed in the avian brain. Furthermore, avian 26RFa stimulates feeding behavior in broiler chicks. This review summarizes the advances in the identification, localization, and functions of 26RFa and its cognate receptor GPR103 in vertebrates and highlights recent progress made in birds.

Gonadotropin-inhibitory hormone (GnIH) was first identified in the Japanese quail as a hypothalamic neuropeptide inhibitor of gonadotropin secretion. Subsequent studies have shown that GnIH is present in the brains of birds including songbirds, and mammals including humans. The identified avian and mammalian GnIH peptides universally possess an LPXRFamide (X = L or Q) motif at their C-termini. Mammalian GnIH peptides are also designated as RFamide-related peptides from their structures. The receptor for GnIH is the G protein-coupled receptor 147 (GPR147), which is thought to be coupled to G(αi) protein. Cell bodies of GnIH neurons are located in the paraventricular nucleus (PVN) in birds and the dorsomedial hypothalamic area (DMH) in mammals. GnIH neurons in the PVN or DMH project to the median eminence to control anterior pituitary function. GPR147 is expressed in the gonadotropes and GnIH suppresses synthesis and release of gonadotropins. It was further shown in immortalized mouse gonadotrope cell line (LβT2 cells) that GnIH inhibits gonadotropin-releasing hormone (GnRH) induced gonadotropin subunit gene transcriptions by inhibiting adenylate cyclase/cAMP/PKA-dependent ERK pathway. GnIH neurons also project to GnRH neurons in the preoptic area, and GnRH neurons express GPR147 in birds and mammals. Accordingly, GnIH may inhibit gonadotropin synthesis and release by decreasing the activity of GnRH neurons as well as directly acting on the gonadotropes. GnIH also inhibits reproductive behavior possibly by acting within the brain. GnIH expression is regulated by a nocturnal hormone melatonin and stress in birds and mammals. Accordingly, GnIH may play a role in translating environmental information to inhibit reproductive physiology and behavior of birds and mammals. Finally, GnIH has therapeutic potential in the treatment of reproductive cycle and hormone-dependent diseases, such as precocious puberty, endometriosis, uterine fibroids, and prostatic and breast cancers.

Two novel RFamide peptides, kisspeptins and gonadotropin-inhibitory hormone (GnIH) are neuropeptides that appear critical in the regulation of the reproductive neuroendocrine axis. GnIH was first identified in avian brain, however, kisspeptins have not been identified in birds. To determine biochemically the presence of kisspeptins and GnIH in the zebra finch, a study was conducted to isolate these two peptides from zebra finch brain. Peptides were isolated by immunoaffinity purification and only one peptide was characterized by mass spectrometry. This peptide was confirmed to be a 12-amino acid sequence with RFamide at its C-terminus; its sequence is SIKPFSNLPLRFamide (zebra finch GnIH). By this approach, however, identification of kisspeptin from zebra finch brain was not achieved. Cloned zebra finch GnIH precursor cDNA encoded three peptides that possess characteristic LPXRFamide (X=L or Q) motifs at the C-termini. In situ hybridization and immunohistochemical analysis revealed the cellular localization of zebra finch GnIH mRNA and peptide in the paraventricular nucleus and the dorsomedial nucleus of the hypothalamus. Fluorescent immunohistochemistry with confocal microscopy indicated that GnIH-immunoreactive (ir) fibers are very close appositions with gonadotropin-releasing hormone-I (GnRH-I) cells. Furthermore GnIH-ir nerve fibers were widely distributed in the multiple brain regions including the septum, preoptic area, median eminence, optic tectum and median eminence. The prominent fibers were seen in the ventral tegmental area, midbrain central gray and dorsal motor nucleus of the vagus in the medulla. Thus, GnIH may participate in not only neuroendocrine functions but also regulation of motivation for social behavior and autonomic mechanisms.

We argue that the intentional control of vocal organ is the most basic predisposition for vocal learning and thus for language acquisition. Anatomical substrates for intentional vocal control are the direct cortical-medullar projections that connect face motor cortecies and the nucleus retro-ambiguus. We ask how such projections may be reinforced in non-vocal learners including macaque monkeys and rodents by behavioral manipulations. We hypothesize how such connections may be prepared in humans.

Bengalese finches, Lonchura striata, are extremely sexually dimorphic in their singing behavior; males sing complex songs, whereas females do not sing at all. This study describes the developmental differentiation of the brain song system in Bengalese finches. Nissl staining was used to measure the volumes of four telencephalic song nuclei: Area X, HVC, the robust nucleus of the arcopallium (RA), and the lateral portion of the magnocellular nucleus of the anterior nidopallium (LMAN). In juveniles (circa 35 days old), Area X and the HVC were well developed in males, while they were absent or not discernable in females. The RA was much larger in males but barely discernable in females. In males, the volumes of Area X and the RA increased further into adulthood, but that of the HVC remained unchanged. The LMAN volume was greater in juveniles than in adults, and there was no difference in the LMAN volume between the sexes. The overall tendency was similar to that described in zebra finches, except for the volume of the RA, where the degree of sexual dimorphism is larger and the timing of differentiation occurs earlier in Bengalese finches. Motor learning of the song continues until day 90 in zebra finches, but up to day 120 in Bengalese finches. Earlier neural differentiation and a longer learning period in Bengalese finches compared with zebra finches may be related to the more elaborate song structures of Bengalese finches.