Babbling opens the sensory phase for imitative vocal learning

Zebra finches, a species of songbirds, learn to sing by creating an auditory template through the memorization of model songs (sensory learning phase) and subsequently translating these perceptual memories into motor skills (sensorimotor learning phase). It has been traditionally believed that babbling in juvenile birds initiates the sensorimotor phase while the sensory phase of song learning precedes the onset of babbling. However, our findings challenge this notion by demonstrating that testosterone-induced premature babbling actually triggers the onset of the sensory learning phase instead. We reveal that juvenile birds must engage in babbling and self-listening to acquire the tutor song as the template. Notably, the sensory learning of the template in songbirds requires motor vocal activity, reflecting the observation that prelinguistic babbling in humans plays a crucial role in auditory learning for language acquisition.

Convergence in hearing-related genes between echolocating birds and mammals

Echolocation, the detection of objects by means of sound waves, has evolved independently in diverse animals. Echolocators include not only mammals such as toothed whales and yangochiropteran and rhinolophoid bats but also Rousettus fruit bats, as well as two bird lineages, oilbirds and swiftlets. In whales and yangochiropteran and rhinolophoid bats, positive selection and molecular convergence has been documented in key hearing-related genes, such as prestin (SLC26A5), but few studies have examined these loci in other echolocators. Here, we examine patterns of selection and convergence in echolocation-related genes in echolocating birds and Rousettus bats. Fewer of these loci were under selection in Rousettus or birds compared with classically recognized echolocators, and elevated convergence (compared to outgroups) was not evident across this gene set. In certain genes, however, we detected convergent substitutions with potential functional relevance, including convergence between Rousettus and classic echolocators in prestin at a site known to affect hair cell electromotility. We also detected convergence between Yangochiroptera, Rhinolophidea, and oilbirds in TMC1, an important mechanosensory transduction channel in vertebrate hair cells, and observed an amino acid change at the same site within the pore domain. Our results suggest that although most proteins implicated in echolocation in specialized mammals may not have been recruited in birds or Rousettus fruit bats, certain hearing-related loci may have undergone convergent functional changes. Investigating adaptations in diverse echolocators will deepen our understanding of this unusual sensory modality.

Differential regulation of Kiss1 gene expression by oestradiol in the hypothalamus of the female Damaraland mole-rat, an induced ovulator

Kisspeptin, a product of the Kiss1 gene is considered a potent stimulator of gonadotropin release, by interacting with its receptor, the G protein-coupled receptor 54. Kiss1 neurons are known to mediate the positive and negative feedback effects of oestradiol on GnRH neurons that control the pulsatile and surge secretion of GnRH. While in spontaneously ovulating mammals the GnRH/LH surge is initiated by a rise in ovarian oestradiol secreted from maturing follicles, in induced ovulators, the primary trigger is the mating stimulus. Damaraland mole rats (Fukomys damarensis) are cooperatively breeding, subterranean rodents that exhibit induced ovulation. We have previously described in this species the distribution and differential expression pattern of Kiss1-expressing neurons in the hypothalamus of males and females. Here we examine whether oestradiol (E2) regulates the hypothalamic Kiss1 expression in a similar way as described for spontaneously ovulating rodent species. By means of in situ hybridisation, we measured Kiss1 mRNA among groups of ovary-intact, ovariectomized (OVX) and OVX females treated with E2 (OVX + E2). In the arcuate nucleus (ARC), Kiss1 expression increased after ovariectomy and decreased with E2 treatment. In the preoptic region, Kiss1 expression after gonadectomy was similar to the level of wild-caught gonad-intact controls, but was dramatically upregulated with E2 treatment. The data suggest that, similar to other species, Kiss1 neurons in the ARC, which are inhibited by E2, play a role in the negative feedback control on GnRH release. The exact role of the Kiss1 neuron population in the preoptic region, which is stimulated by E2, remains to be determined.

Testosterone coordinates gene expression across different tissues to produce carotenoid-based red ornamentation

Carotenoid pigments underlie most of the red, orange, and yellow visual signals used in mate choice in vertebrates. However, many of the underlying processes surrounding the production of carotenoid-based traits remain unclear due to the complex nature of carotenoid uptake, metabolism, and deposition across tissues. Here, we leverage the ability to experimentally induce the production of a carotenoid-based red plumage patch in the red-backed fairywren (Malurus melanocephalus), a songbird in which red plumage is an important male sexual signal. We experimentally elevated testosterone in unornamented males lacking red plumage to induce the production of ornamentation, and compared gene expression in both the liver and feather follicles between unornamented control males, testosterone-implanted males, and naturally ornamented males. We show that testosterone upregulates the expression of CYP2J19, a gene known to be involved in ketocarotenoid metabolism, and a putative carotenoid processing gene (ELOVL6) in the liver, and also regulates the expression of putative carotenoid transporter genes in red feather follicles on the back, including ABCG1. In black feathers, carotenoid-related genes are downregulated and melanin genes upregulated, but we find that carotenoids are still present in the feathers. This may be due to the activity of the carotenoid-cleaving enzyme BCO2 in black feathers. Our study provides a first working model of a pathway for carotenoid-based trait production in free-living birds, implicates testosterone as a key regulator of carotenoid-associated gene expression, and suggests hormones may coordinate the many processes that underlie the production of these traits across multiple tissues.

Sparse ensemble neural code for a complete vocal repertoire

The categorization of animal vocalizations into distinct behaviorally relevant groups for communication is an essential operation that must be performed by the auditory system. This auditory object recognition is a difficult task that requires selectivity to the group identifying acoustic features and invariance to renditions within each group. We find that small ensembles of auditory neurons in the forebrain of a social songbird can code the bird's entire vocal repertoire (∼10 call types). Ensemble neural discrimination is not, however, correlated with single unit selectivity, but instead with how well the joint single unit tunings to characteristic spectro-temporal modulations span the acoustic subspace optimized for the discrimination of call types. Thus, akin to face recognition in the visual system, call type recognition in the auditory system is based on a sparse code representing a small number of high-level features and not on highly selective grandmother neurons.

Vision and vocal communication guide three-dimensional spatial coordination of zebra finches during wind-tunnel flights

Animal collective motion is a natural phenomenon readily observable in various taxa. Although theoretical models can predict the macroscopic pattern of group movements based on the relative spatial position of group members, it is poorly understood how group members exchange directional information, which enables the spatial coordination between individuals during collective motion. To test if vocalizations emitted during flocking flight are used by birds to transmit directional information between group members, we recorded vocal behaviour, head orientation and spatial position of each individual in a small flock of zebra finches (Taeniopygia guttata) flying in a wind tunnel. We found that the finches can use both visual and acoustic cues for three-dimensional flock coordination. When visual information is insufficient, birds can increasingly exploit active vocal communication to avoid collisions with flock mates. Our study furthers the mechanistic understanding of collective motion in birds and highlights the impact interindividual vocal interactions can have on group performances in these animals.

Zebra finches flying in a wind tunnel use both vocal and visual communication to orientate themselves within the flock, and are able to enhance their use of one form of communication over another depending on circumstance.

Impact of serotonin transporter (SERT) binding affinity on the risk of libido disorders related to antidepressants

Introduction

Sexual dysfunction is a frequent adverse drug reaction (ADR) of antidepressants that considerably affects quality of life and adherence to therapy. We previously investigated the potential underlying neurofunctional mechanisms by neuroimaging methods and revealed a dampening of the dopaminergic mesolimbic-mesocortical reward system along with decreased sexual functioning under serotonergic antidepressants compared to placebo.

Objectives

Within a combined pharmacoepidemiologic and pharmacodynamic approach, we examined the association between serotonin transporter (SERT) affinity of various antidepressants and corresponding alterations in sexual desire as ADR.

Methods

Using disproportionality analyses, reporting odds ratios (RORs) were calculated for reports indicating decreased sexual desire as ADR under the antidepressants. The data were extracted from the WHO global database of individual case safety reports VigiBase and several MedDRA terms were grouped for “Sexual Desire Disorders”. For the pharmacodynamic assessment, we calculated Pearson correlation coefficients between SERT affinity and corresponding RORs

Results

16 signals were detected for “Sexual Desire Disorders”. We observed a statistically significant (r (20) =. 65, p = 0.001) association between SERT affinity and decreased sexual desire. Higher SERT affinity was associated with higher risk of sexual desire.

Conclusions

While sexual dysfunctions under serotonergic medication were previously described, we now elaborated that in particular attenuated sexual desire as ADR is associated with SERT affinity of the antidepressant. These results strengthen our previously described neurofunctional model regarding sexual dysfunction under antidepressant medication and indicate that the specific SERT affinity of the antidepressant drug should be considered in clinical practice to minimize the risk of this ADR.

Disclosure

No significant relationships.

Drug-induced liver injury in association with antipsychotics

Introduction

Drug-induced liver injury is one of the leading causes for acute liver failure and drug withdrawal after marketing approval. One important risk factor is the extent of exposure of the hepatocytes to a substance, either by high doses or by long-term medication. In many psychiatric diseases, like schizophrenia long-term use of drugs is common. However, systematic data on the hepatotoxic potential of antipsychotics is scarce.

Objectives

To perform an explorative analysis of pharmacovigilance data on the risk of hepatotoxicity related to the use of antipsychotics.

Methods

We conducted an explorative case/non-case study based on data from VigiBase for 30 antipsychotics marketed in the European Union. Reporting odds ratios were calculated for antipsychotics associated with the SMQ “Drug related hepatic disorders - comprehensive search” and the SMQ “Drug related hepatic disorders - severe events only”.

Results

We found several associations of antipsychotics with drug-induced liver injury including associations with severe events. 17/30 antipsychotics were associated with “Drug related hepatic disorders - comprehensive search”, and for 10/30 substances were associated with severe hepatic events.

Conclusions

Several antipsychotics are associated with the risk for hepatotoxic side effects, even severe ones. Further research is warranted on patient and substance-dependent risk factors.

Disclosure

No significant relationships.

Retinal single-layer analysis with optical coherence tomography (OCT) in schizophrenia spectrum disorder

Introduction

Volume reductions in brain structures of patients with schizophrenia spectrum disorder (SSD) have repeatedly been found in voxel-based morphometry MRI studies. Hence, an underlying neurodegenerative etiological component of SSD is currently being discussed. In recent years, the imaging method of optical coherence tomography (OCT) has shown its potential in evaluating structural changes in the retina in patients with confirmed neurodegenerative disorders, providing a window into the brain.

Objectives

To evaluate potential differences in measurements of retinal layers between patients with schizophrenia spectrum disorder and healthy controls with OCT.

Methods

Twenty-six patients with schizophrenia or schizoaffective disorder and 23 age- and sex-matched healthy controls were examined with the Heidelberg Spectralis OCT system to derive a single-layer analysis of both retinas. The segmentation of retinal layers was manually corrected to minimize artifacts and software imprecisions.

Results

Compared to the control group, SSD patients showed reduced thickness and volume measurements for nearly all retinal layers, and these differences reached significance for macular volume, macular thickness, retinal nerve fiber layer (RNFL) and inner nucleiform layer (INL). Furthermore, a significant correlation between the duration of illness and the total volume of the RNFL was found.

Conclusions

Our OCT measurements demonstrate reduced single retinal layer thickness in patients with SSD. In the context of the MRI volume changes, our results provide further evidence that structural changes seen in the brain of patients are also observable in the retina, potentially allowing further insights into the different components of the nervous system that are altered in this highly etiologically complex disorder.

Disclosure

No significant relationships.

Extensive GJD2 Expression in the Song Motor Pathway Reveals the Extent of Electrical Synapses in the Songbird Brain

Birdsong is a precisely timed animal behavior. The connectivity of song premotor neural networks has been proposed to underlie the temporal patterns of neuronal activity that control vocal muscle movements during singing. Although the connectivity of premotor nuclei via chemical synapses has been characterized, electrical synapses and their molecular identity remain unexplored. We show with in situ hybridizations that GJD2 mRNA, coding for the major channel-forming electrical synapse protein in mammals, connexin 36, is expressed in the two nuclei that control song production, HVC and RA from canaries and zebra finches. In canaries' HVC, GJD2 mRNA is extensively expressed in GABAergic and only a fraction of glutamatergic cells. By contrast, in RA, GJD2 mRNA expression is widespread in glutamatergic and GABAergic neurons. Remarkably, GJD2 expression is similar in song nuclei and their respective embedding brain regions, revealing the widespread expression of GJD2 in the avian brain. Inspection of a single-cell sequencing database from zebra and Bengalese finches generalizes the distributions of electrical synapses across cell types and song nuclei that we found in HVC and RA from canaries, reveals a differential GJD2 mRNA expression in HVC glutamatergic subtypes and its transient increase along the neurogenic lineage. We propose that songbirds are a suitable model to investigate the contribution of electrical synapses to motor skill learning and production.

An Unbiased Molecular Approach Using 3'-UTRs Resolves the Avian Family-Level Tree of Life

Presumably, due to a rapid early diversification, major parts of the higher-level phylogeny of birds are still resolved controversially in different analyses or are considered unresolvable. To address this problem, we produced an avian tree of life, which includes molecular sequences of one or several species of ∼90% of the currently recognized family-level taxa (429 species, 379 genera) including all 106 family-level taxa of the nonpasserines and 115 of the passerines (Passeriformes). The unconstrained analyses of noncoding 3-prime untranslated region (3′-UTR) sequences and those of coding sequences yielded different trees. In contrast to the coding sequences, the 3′-UTR sequences resulted in a well-resolved and stable tree topology. The 3′-UTR contained, unexpectedly, transcription factor binding motifs that were specific for different higher-level taxa. In this tree, grebes and flamingos are the sister clade of all other Neoaves, which are subdivided into five major clades. All nonpasserine taxa were placed with robust statistical support including the long-time enigmatic hoatzin (Opisthocomiformes), which was found being the sister taxon of the Caprimulgiformes. The comparatively late radiation of family-level clades of the songbirds (oscine Passeriformes) contrasts with the attenuated diversification of nonpasseriform taxa since the early Miocene. This correlates with the evolution of vocal production learning, an important speciation factor, which is ancestral for songbirds and evolved convergent only in hummingbirds and parrots. As 3′-UTR-based phylotranscriptomics resolved the avian family-level tree of life, we suggest that this procedure will also resolve the all-species avian tree of life

The Gene Expression Profile of the Song Control Nucleus HVC Shows Sex Specificity, Hormone Responsiveness, and Species Specificity Among Songbirds

Singing occurs in songbirds of both sexes, but some species show typical degrees of sex-specific performance. We studied the transcriptional sex differences in the HVC, a brain nucleus critical for song pattern generation, of the forest weaver (Ploceus bicolor), the blue-capped cordon-bleu (Uraeginthus cyanocephalus), and the canary (Serinus canaria), which are species that show low, medium, and high levels of sex-specific singing, respectively. We observed persistent sex differences in gene expression levels regardless of the species-specific sexual singing phenotypes. We further studied the HVC transcriptomes of defined phenotypes of canary, known for its testosterone-sensitive seasonal singing. By studying both sexes of canaries during both breeding and non-breeding seasons, non-breeding canaries treated with testosterone, and spontaneously singing females, we found that the circulating androgen levels and sex were the predominant variables associated with the variations in the HVC transcriptomes. The comparison of natural singing with testosterone-induced singing in canaries of the same sex revealed considerable differences in the HVC transcriptomes. Strong transcriptional changes in the HVC were detected during the transition from non-singing to singing in canaries of both sexes. Although the sex-specific genes of singing females shared little resemblance with those of males, our analysis showed potential functional convergences. Thus, male and female songbirds achieve comparable singing behaviours with sex-specific transcriptomes.

Highly Efficient Genome Modification of Cultured Primordial Germ Cells with Lentiviral Vectors to Generate Transgenic Songbirds

The ability to genetically manipulate organisms has led to significant insights into functional genomics in many species. In birds, manipulation of the genome is hindered by the inaccessibility of the one-cell embryo. During embryonic development, avian primordial germ cells (PGCs) migrate through the bloodstream and reach the gonadal anlage, where they develop into mature germ cells. Here, we explored the use of PGCs to produce transgenic offspring in the zebra finch, which is a major animal model for sexual brain differentiation, vocal learning, and vocal communication. Zebra finch PGCs (zfPGCs) obtained from embryonic blood significantly proliferated when cultured in an optimized culture medium and conserved the expression of germ and stem cell markers. Transduction of cultured zfPGCs with lentiviral vectors was highly efficient, leading to strong expression of the enhanced green fluorescent protein. Transduced zfPGCs were injected into the host embryo and transgenic songbirds were successfully generated.

Neuroendocrine patterns underlying seasonal song and year-round territoriality in male black redstarts

BACKGROUND

The connection between testosterone and territoriality in free-living songbirds has been well studied in a reproductive context, but less so outside the breeding season. To assess the effects of seasonal androgenic action on territorial behavior, we analyzed vocal and non-vocal territorial behavior in response to simulated territorial intrusions (STIs) during three life-cycle stages in free-living male black redstarts: breeding, molt and nonbreeding. Concurrently, we measured changes in circulating testosterone levels, as well as the mRNA expression of androgen and estrogen receptors and aromatase in the preoptic, hypothalamic and song control brain areas that are associated with social and vocal behaviors.

RESULTS

Territorial behavior and estrogen receptor expression in hypothalamic areas did not differ between stages. But plasma testosterone was higher during breeding than during the other stages, similar to androgen receptor and aromatase expression in the preoptic area. The expression of androgen receptors in the song control nucleus HVC was lower during molt when birds do not sing or sing rarely, but similar between the breeding and the nonbreeding stage. Nevertheless, some song spectral features and the song repertoire differed between breeding and nonbreeding. Territorial behavior and song rate correlated with the expression of steroid receptors in hypothalamic areas, and in the song control nucleus lMAN.

CONCLUSIONS

Our results demonstrate seasonal modulation of song, circulating testosterone levels, and brain sensitivity to androgens, but a year-round persistency of territorial behavior and estrogen receptor expression in all life-cycle stages. This suggests that seasonal variations in circulating testosterone concentrations and brain sensitivity to androgens is widely uncoupled from territorial behavior and song activity but might still affect song pattern. Our study contributes to the understanding of the complex comparative neuroendocrinology of song birds in the wild.

Functional differences in the hypothalamic-pituitary-gonadal axis are associated with alternative reproductive tactics based on an inversion polymorphism

The evolution of social behavior depends on genetic changes, yet, how genomic variation manifests itself in behavioral diversity is still largely unresolved. Chromosomal inversions can play a pivotal role in producing distinct behavioral phenotypes, in particular, when inversion genes are functionally associated with hormone synthesis and signaling. Male ruffs exhibit alternative reproductive tactics (ARTs) with an autosomal inversion determining two alternative morphs with clear behavioral and hormonal differences from the ancestral morph. We investigated hormonal and transcriptomic differences in the pituitary and gonads. Using a GnRH challenge, we found that the ability to synthesize testosterone in inversion carriers is severely constrained, whereas the synthesis of androstenedione, a testosterone precursor, is not. Inversion morphs were able to produce a transient increase in androstenedione following the GnRH injection, supporting the view that pituitary sensitivity to GnRH is comparable to that of the ancestral morph. We then performed gene expression analyses in a second set of untreated birds and found no evidence of alterations to pituitary sensitivity, gonadotropin production or gonad sensitivity to luteinizing hormone or follicle-stimulating hormone across morphs. Inversion morphs also showed reduced progesterone receptor expression in the pituitary. Strikingly, in the gonads, inversion morphs over-expressed STAR, a gene that is located outside of the inversion and responsible for providing the cholesterol substrate required for the synthesis of sex hormones. In conclusion, our results suggest that the gonads determine morph-specific differences in hormonal regulation.

Life-Stage Dependent Plasticity in the Auditory System of a Songbird Is Signal and Emitter-Specific

Social animals flexibly use a variety of vocalizations to communicate in complex and dynamic environments. However, it remains unknown whether the auditory perception of different vocalizations changes according to the ecological context. By using miniature wireless devices to synchronously record vocal interactions and local neural activity in freely-behaving zebra finches in combination with playback experiments, we investigate whether the auditory processing of vocalizations changes across life-history stages. We show that during breeding, females (but not males) increase their estrogen levels and reply faster to their mates when interacting vocally. These changes are associated with an increase in the amplitude of the female’s neural auditory responses. Furthermore, the changes in auditory response are not general, but specific to a subset of functionally distinct vocalizations and dependent on the emitter’s identity. These results provide novel insights into auditory plasticity of communication systems, showing that the perception of specific signals can shift according to ecologically-determined physiological states.

Fast Retrograde Access to Projection Neuron Circuits Underlying Vocal Learning in Songbirds

Understanding the structure and function of neural circuits underlying speech and language is a vital step toward better treatments for diseases of these systems. Songbirds, among the few animal orders that share with humans the ability to learn vocalizations from a conspecific, have provided many insights into the neural mechanisms of vocal development. However, research into vocal learning circuits has been hindered by a lack of tools for rapid genetic targeting of specific neuron populations to meet the quick pace of developmental learning. Here, we present a viral tool that enables fast and efficient retrograde access to projection neuron populations. In zebra finches, Bengalese finches, canaries, and mice, we demonstrate fast retrograde labeling of cortical or dopaminergic neurons. We further demonstrate the suitability of our construct for detailed morphological analysis, for in vivo imaging of calcium activity, and for multi-color brainbow labeling.

Düring et al. describe a fast and efficient viral vector to dissect structure and function of neural circuits underlying learned vocalizations in songbirds. The AAV variant provides retrograde access to projection neuron circuits, including dopaminergic pathways in songbirds and additionally in mice, and allows for retrograde calcium imaging and multispectral brainbow labeling.

The neuroleptic malignant syndrome-a systematic case series analysis focusing on therapy regimes and outcome

INTRODUCTION

Neuroleptic malignant syndrome (NMS) is a rare, potentially life-threatening antipsychotic-associated disorder that requires an efficient and timely therapy. The aim of the study was to compare the effectiveness of different NMS therapies and to analyze its outcome depending on NMS severity.

METHOD

Systematic search for NMS cases in biomedical databases. The focus of the analysis was on therapy with dantrolene, bromocriptine, and electroconvulsive therapy (ECT) when each was compared with symptomatic therapy. Primary outcomes were the survival rate and the duration of treatment.

RESULT

405 case reports were included. Overall, no statistically significant differences regarding mortality rate or duration of treatment were found between dantrolene, bromocriptine, or ECT compared to supportive care. A subgroup analysis regarding NMS severity showed that the mortality under specific NMS pharmacotherapy (dantrolene, bromocriptine) and under ECT was significantly lower than under purely symptomatic therapy in severe NMS (P = 0.018). The difference was not significant in mild and moderate cases.

DISCUSSION

An overall superiority of the specific NMS therapy (dantrolene, bromocriptine, and ECT) was not found in this study. When regarding severity classification, specific therapies were superior but only in severe cases, and ECT showed the lowest mortality rate. In previous case series, an effect on survival or the duration of the disease could only be observed in part for specific therapies, but the evidence available is inconsistent. The results of this study support our hypothesis that NMS treatment with dantrolene, bromocriptine, and ECT is advantageous over purely symptomatic therapy in severe NMS cases.

Neurotelemetry Reveals Putative Predictive Activity in HVC during Call-Based Vocal Communications in Zebra Finches

Premotor predictions facilitate vocal interactions. Here, we study such mechanisms in the forebrain nucleus HVC (proper name), a cortex-like sensorimotor area of songbirds, otherwise known for being essential for singing in zebra finches. To study the role of the HVC in calling interactions between male and female mates, we used wireless telemetric systems for simultaneous measurement of neuronal activity of male zebra finches and vocalizations of males and females that freely interact with each other. In a non-social context, male HVC neurons displayed stereotypic premotor activity in relation to active calling and showed auditory-evoked activity to hearing of played-back female calls. In a social context, HVC neurons displayed auditory-evoked activity to hearing of female calls only if that neuron showed activity preceding the upcoming female calls. We hypothesize that this activity preceding the auditory-evoked activity in the male HVC represents a neural correlate of behavioral anticipation, predictive activity that helps to coordinate vocal communication between social partners.SIGNIFICANCE STATEMENT Most social-living vertebrates produce large numbers of calls per day, and the calls have prominent roles in social interactions. Here, we show neuronal mechanisms that are active during call-based vocal communication of zebra finches, a highly social songbird species. HVC, a forebrain nucleus known for its importance in control of learned vocalizations of songbirds, displays predictive activity that may enable the male to adjust his own calling pattern to produce very fast sequences of male female call exchanges.

The hummingbird syrinx morphome: a detailed three-dimensional description of the black jacobin’s vocal organ

Background

The ability to imitate sounds depends on a process called vocal production learning, a rare evolutionary trait. In addition to the few mammalian groups that possess this ability, vocal production learning has evolved independently in three avian clades: songbirds, parrots, and hummingbirds. Although the anatomy and mechanisms of sound production in songbirds are well understood, little is known about the hummingbird’s vocal anatomy.

Results

We use high-resolution micro-computed tomography (μCT) and microdissection to reveal the three-dimensional structure of the syrinx, the vocal organ of the black jacobin (Florisuga fusca), a phylogenetically basal hummingbird species. We identify three features of the black jacobin’s syrinx: (i) a shift in the position of the syrinx to the outside of the thoracic cavity and the related loss of the sterno-tracheal muscle, (ii) complex intrinsic musculature, oriented dorso-ventrally, and (iii) ossicles embedded in the medial vibratory membranes.

Conclusions

The extra-thoracic placement of the black jacobin’s syrinx and the dorso-ventrally oriented musculature likely aid to uncoupling syrinx movements from extensive flight-related thorax constraints. The syrinx morphology further allows for vibratory decoupling, precise control of complex acoustic parameters, and a large motor redundancy that may be key biomechanical factors leading to acoustic complexity and thus facilitating the occurrence of vocal production learning.

Vocal tract anatomy of king penguins: morphological traits of two-voiced sound production

BACKGROUND

The astonishing variety of sounds that birds can produce has been the subject of many studies aiming to identify the underlying anatomical and physical mechanisms of sound production. An interesting feature of some bird vocalisations is the simultaneous production of two different frequencies. While most work has been focusing on songbirds, much less is known about dual-sound production in non-passerines, although their sound production organ, the syrinx, would technically allow many of them to produce "two voices". Here, we focus on the king penguin, a colonial seabird whose calls consist of two fundamental frequency bands and their respective harmonics. The calls are produced during courtship and for partner and offspring reunions and encode the birds' identity. We dissected, μCT-scanned and analysed the vocal tracts of six adult king penguins from Possession Island, Crozet Archipelago.

RESULTS

King penguins possess a bronchial type syrinx that, similarly to the songbird's tracheobronchial syrinx, has two sets of vibratory tissues, and thus two separate sound sources. Left and right medial labium differ consistently in diameter between 0.5 and 3.2%, with no laterality between left and right side. The trachea has a conical shape, increasing in diameter from caudal to cranial by 16%. About 80% of the king penguins' trachea is medially divided by a septum consisting of soft elastic tissue (septum trachealis medialis).

CONCLUSIONS

The king penguins' vocal tract appears to be mainly adapted to the life in a noisy colony of a species that relies on individual vocal recognition. The extent between the two voices encoding for individuality seems morphologically dictated by the length difference between left and right medial labium. The septum trachealis medialis might support this extent and could therefore be an important anatomical feature that aids in the individual recognition process.

Characteristics of song, brain-anatomy and blood androgen levels in spontaneously singing female canaries

Females of many northern temperate songbird species sing sporadically. However, detailed descriptions of female song are rare. Here we report a detailed analysis of song in a small number of spontaneously-singing female domesticated canaries (Serinus canaria) under non-breeding, laboratory conditions in a large population of domesticated birds. In-depth analysis showed that these females sang rarely, and the spontaneous songs varied between and within birds over time. Furthermore, spontaneous female songs were distinct from songs of testosterone-induced singing female canaries and from songs of male canaries in both temporal and spectral features. Singing females had significantly elevated plasma androgen levels and a larger size of the major song controlling brain nuclei HVC (used as a proper name) and the robust nucleus of the arcopallium (RA) than non-singing females housed under similar conditions. The sporadically observed production of song and accompanying differences in brain anatomy in female canaries may thus depend on minute intraspecific differences in androgen levels.

Accelerated redevelopment of vocal skills is preceded by lasting reorganization of the song motor circuitry

Complex motor skills take considerable time and practice to learn. Without continued practice the level of skill performance quickly degrades, posing a problem for the timely utilization of skilled motor behaviors. Here we quantified the recurring development of vocal motor skills and the accompanying changes in synaptic connectivity in the brain of a songbird, while manipulating skill performance by consecutively administrating and withdrawing testosterone. We demonstrate that a songbird with prior singing experience can significantly accelerate the re-acquisition of vocal performance. We further demonstrate that an increase in vocal performance is accompanied by a pronounced synaptic pruning in the forebrain vocal motor area HVC, a reduction that is not reversed when birds stop singing. These results provide evidence that lasting synaptic changes in the motor circuitry are associated with the savings of motor skills, enabling a rapid recovery of motor performance under environmental time constraints.

The Genome of Blue-Capped Cordon-Bleu Uncovers Hidden Diversity of LTR Retrotransposons in Zebra Finch

Avian genomes have perplexed researchers by being conservative in both size and rearrangements, while simultaneously holding the blueprints for a massive species radiation during the last 65 million years (My). Transposable elements (TEs) in bird genomes are relatively scarce but have been implicated as important hotspots for chromosomal inversions. In zebra finch (Taeniopygia guttata), long terminal repeat (LTR) retrotransposons have proliferated and are positively associated with chromosomal breakpoint regions. Here, we present the genome, karyotype and transposons of blue-capped cordon-bleu (Uraeginthus cyanocephalus), an African songbird that diverged from zebra finch at the root of estrildid finches 10 million years ago (Mya). This constitutes the third linked-read sequenced genome assembly and fourth in-depth curated TE library of any bird. Exploration of TE diversity on this brief evolutionary timescale constitutes a considerable increase in resolution for avian TE biology and allowed us to uncover 4.5 Mb more LTR retrotransposons in the zebra finch genome. In blue-capped cordon-bleu, we likewise observed a recent LTR accumulation indicating that this is a shared feature of Estrildidae. Curiously, we discovered 25 new endogenous retrovirus-like LTR retrotransposon families of which at least 21 are present in zebra finch but were previously undiscovered. This highlights the importance of studying close relatives of model organisms.

Tissue Clearing and Light Sheet Microscopy: Imaging the Unsectioned Adult Zebra Finch Brain at Cellular Resolution

The inherent complexity of brain tissue, with brain cells intertwining locally and projecting to distant regions, has made three-dimensional visualization of intact brains a highly desirable but challenging task in neuroscience. The natural opaqueness of tissue has traditionally limited researchers to techniques short of single cell resolution such as computer tomography or magnetic resonance imaging. By contrast, techniques with single-cell resolution required mechanical slicing into thin sections, which entails tissue distortions that severely hinder accurate reconstruction of large volumes. Recent developments in tissue clearing and light sheet microscopy have made it possible to investigate large volumes at micrometer resolution. The value of tissue clearing has been shown in a variety of tissue types and animal models. However, its potential for examining the songbird brain remains unexplored. Songbirds are an established model system for the study of vocal learning and sensorimotor control. They share with humans the capacity to adapt vocalizations based on auditory input. Song learning and production are controlled in songbirds by the song system, which forms a network of interconnected discrete brain nuclei. Here, we use the CUBIC and iDISCO+ protocols for clearing adult songbird brain tissue. Combined with light sheet imaging, we show the potential of tissue clearing for the investigation of connectivity between song nuclei, as well as for neuroanatomy and brain vasculature studies.

Expansion Light Sheet Microscopy Resolves Subcellular Structures in Large Portions of the Songbird Brain

Expansion microscopy and light sheet imaging (ExLSM) provide a viable alternative to existing tissue clearing and large volume imaging approaches. The analysis of intact volumes of brain tissue presents a distinct challenge in neuroscience. Recent advances in tissue clearing and light sheet microscopy have re-addressed this challenge and blossomed into a plethora of protocols with diverse advantages and disadvantages. While refractive index matching achieves near perfect transparency and allows for imaging at large depths, the resolution of cleared brains is usually limited to the micrometer range. Moreover, the often long and harsh tissue clearing protocols hinder preservation of native fluorescence and antigenicity. Here we image large expanded brain volumes of zebra finch brain tissue in commercially available light sheet microscopes. Our expansion light sheet microscopy (ExLSM) approach presents a viable alternative to many clearing and imaging methods because it improves on tissue processing times, fluorophore compatibility, and image resolution.

Avian yolk androgens are metabolized instead of taken up by the embryo during the first days of incubation

Several studies show effects of yolk androgens in avian eggs on the phenotype of the offspring. Yolk hormone concentrations decline strongly already in the first few days of incubation. Although early embryonic uptake of yolk androgens is suggested by the presence of radioactivity in the embryo when eggs are injected with radiolabelled androgens, these studies do not verify the chemical identity of radioactive compound(s), while it is known that these androgens can be metabolized substantially. By using stable isotope labelled testosterone and androstenedione in combination with mass spectrometry, enabling verification of the exact molecular identity of labelled compounds in the embryo, we found that after five days of incubation the androgens are not taken up by the embryo. Yet their concentrations in the entire yolk-albumen homogenates decline strongly, even when corrected for dilution by albumen and water. Our results indicate metabolism of maternal androgens, very likely to 5β-androstane-3α,17β-diol, etiocholanolone, and their conjugated forms. The results imply that the effects of increased exposure of the embryo to maternal androgens either take place before this early conversion or are mediated by these metabolites with a so far unknown function, opening new avenues for understanding hormone mediated maternal effects in vertebrates.

Two macaw species can learn to solve an optimised two-trap problem, but without functional causal understanding

The trap-tube paradigm is a useful reference for judging whether a species is likely to use advanced physical causal cognition, however it does not have a standardised format. In this study, the design of an optimised two trap-table is described and is then tested on two species of macaw: Ara ambiguus and Ara glaucogularis. Multiple subjects of both species learned a successful method to solve an initial trap-problem and some transferred this success to other apparatus presented. However this transfer was likely achieved without a functional physical understanding of the task. The macaws probably have a preference to use learned rules based on arbitrary properties to solve the trap-problem. We conclude that this setup of the two-trap-problem is a viable benchmark that could be administered to a variety of species with very little modification, thus paving the way for more directly comparative studies.

Neuromuskuläre Erkrankungen

Funktionsstörungen der verschiedenen Komponenten motorischer Einheiten führen zu neuromuskulären Erkrankungen (NME), bei denen das zentrale, sensible oder auch autonome Nervensystem und andere Organsysteme mitbetroffen sein können. Allen NME gemein ist eine Verminderung der groben Kraft mit meist progredienter degenerativer Muskelatrophie.

Early embryonic modification of maternal hormones differs systematically among embryos of different laying order: A study in birds

Vertebrate embryos are exposed to maternal hormones that can profoundly affect their later phenotype. Although it is known that the embryo can metabolize these maternal hormones, the metabolic outcomes, their quantitative dynamics and timing are poorly understood. Moreover, it is unknown whether embryos can adjust their metabolic activity to, for example, hormones or other maternal signals. We studied the dynamics of maternal steroids in fertilized and unfertilized rock pigeon eggs during early incubation. Embryos of this species are naturally exposed to different amounts of maternal steroids in the egg according to their laying position, which provides a natural context to study differential embryonic regulation of the maternal signals. We used mass spectrometric analyses to map changes in the androgen and estrogen pathways of conversion. We show that the active hormones are heavily metabolized only in fertilized eggs, with a corresponding increase in supposedly less potent metabolites already within one-fourth of total incubation period. Interestingly, the rate of androgen metabolism was different between embryos in different laying positions. The results also warrant a re-interpretation of the timing of hormone mediated maternal effects and the role of the supposedly biologically inactive metabolites. Furthermore, the results also provide a potential solution as to how the embryo can prevent maternal steroids in the egg from interfering with its sexual differentiation processes as we show that the embryo can metabolize most of the maternal steroids before sexual differentiation starts.

Seasonality at the equator: isotope signatures and hormonal correlates of molt phenology in a non-migratory Amazonian songbird

BACKGROUND

Birds, across their annual cycle, progress through sequences of life-history stages such as reproduction and molt. The mechanisms that control annual avian itineraries involve endocrine responses triggered by seasonal environmental factors, including changes in resource availability and/or photoperiod. However, at equatorial latitudes birds are exposed to different degrees of seasonality, and the mechanisms underlying phenology of birds near the equator remain less explored. We studied the silver-beaked tanager, an endemic Amazonian songbird, from an equatorial lowland population. Remarkably, in this species, song behavior has been shown to be seasonally aligned to minimal changes in day length near the equator. Here, we aimed to further explore the phenology of silver-beaked tanagers by assessing shifts of food sources utilization as potential ultimate factors. We measured triple isotopic tracers of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) in blood and feathers of birds throughout a whole year. In addition, we assessed the degree of seasonality in the molting activity, in relation to circulating levels of corticosterone, as well as to testosterone as a proxy of the reproductive condition of males.

RESULTS

There was important seasonal variation of δ34S values in relation to rainfall patterns and changes in estuarine water composition. Despite the seasonal rainfall, we found no substantial variation in the foraging ecology of birds over seasons. This was accompanied by uniform levels of corticosterone throughout the year, probably associated with the absence of drastic seasonal resource shortages. Even so, silver-beaked tanagers showed a marked seasonal molting schedule, which was related to variation in the circulating levels of both corticosterone and testosterone.

CONCLUSIONS

These findings suggest that foraging niche is not life history stage-dependent in silver-beaked tanagers, and highlight rainfall as an important environmental cue for bird phenology. Our stable isotope results encourage further studies addressing the influence of estuarine water dynamics on bird timing. In addition, the results suggest a primary role of steroid hormones in regulating seasonal life history stages under the absence of a marked photoperiod. Contrary to what might be expected for a tropical songbird, our physiological data in silver-beaked tanagers do not support reproduction-molt overlapping.

Emotional responses to conspecific distress calls are modulated by affiliation in cockatiels (Nymphicus hollandicus)

Vocal communication is used across the animal kingdom to transfer information from emitters to receivers, such as size, sex, age, dominance status or even emotional states. The transmission of an emotional state from one individual to another is called "emotional contagion" and is classified as the first level of empathy. Emotional contagion is thought to be stronger between familiar individuals. While affiliation represents a stronger relation between individuals than mere familiarity, it remains understudied whether affiliation modulates emotional reactions as well. Using cockatiels (Nymphicus hollandicus), we played back three types of audio stimuli to individual birds: a partner's distress call (emitted when birds are caught or forcibly restrained), a non-partner's distress call, and a control sound (white noise). The calls were recorded from familiar birds with either low (non-partners) or high levels of affiliation (partners). The subjects' response was scored using four behavioural parameters: the time spent near the loudspeaker, the amount of movements, the number of calls emitted, and the position of the crest. Across all variables, birds were more attentive and active when confronted to distress calls compared to control sounds, particularly when the distress call was emitted from a partner rather than a non-partner. These results raise the possibility that distress calls do not only function as a stimulus-triggering automatic reaction in cockatiels but also transmit emotions. Moreover, affiliation enhanced emotional reactions to conspecific distress calls. Our data provides first insights into the mechanisms of emotional contagion in parrots.

Couples showing off: Audience promotes both male and female multimodal courtship display in a songbird

Social environments can shape animal communication. Although mutual courtship displays are generally thought to function in private communication between a male and a female, we provide experimental evidence that they work in a broader social context than previously thought. We examined the audience effect on mutual courtship in blue-capped cordon-bleus, a socially monogamous songbird. This species is characterized by conspicuous courtship shared between sexes: Both sexes sing songs and sometimes add a unique dance display that looks like human tap dancing. We found that in both sexes, multimodal courtship displays (song accompanied by dance) were promoted in the presence of an audience, especially if it was the opposite sex. In contrast, unimodal displays (song without dance) were suppressed by audiences. Because birds directed the courtship dancing toward their partners (but not the audience), multimodal courtship displays are likely meant to advertise their current mating status to other cordon-bleus.

Androgen and estrogen sensitivity of bird song: a comparative view on gene regulatory levels

Singing of songbirds is sensitive to testosterone and its androgenic and estrogenic metabolites in a species-specific way. The hormonal effects on song pattern are likely mediated by androgen receptors (AR) and estrogen receptor alpha (ERα), ligand activated transcription factors that are expressed in neurons of various areas of the songbirds' vocal control circuit. The distribution of AR in this circuit is rather similar between species while that of ERα is species variant and concerns a key vocal control area, the HVC (proper name). We discuss the regulation of the expression of the cognate AR and ERα and putative splice variants. In particular, we suggest that transcription factor binding sites in the promoter of these receptors differ between bird species. Further, we suggest that AR- and ERα-dependent gene regulation in vocal areas differs between species due to species-specific DNA binding sites of putative target genes that are required for the transcriptional activity of the receptors. We suggest that species differences in the distribution of AR and ERα in vocal areas and in the genomic sensitivity to these receptors contribute to species-specific hormonal regulation of the song.

Neuromuscular mechanisms of an elaborate wing display in the golden-collared manakin (Manacus vitellinus)

Many species perform elaborate physical displays to court mates and compete with rivals, but the biomechanical mechanisms underlying such behavior are poorly understood. We address this issue by studying the neuromuscular origins of display behavior in a small tropical passerine bird, the golden-collared manakin (Manacus vitellinus). Males of this species court females by dancing around the forest floor and rapidly snapping their wings together above their back. Using radio-telemetry, we collected electromyographic (EMG) recordings from the three main muscles that control avian forelimb movement, and found how these different muscles are activated to generate various aspects of display behavior. The muscle that raises the wing (supracoracoideus, SC) and the primary muscle that retracts the wing (scapulohumeralis caudalis, SH) were activated during the wing-snap, whereas the pectoralis (PEC), the main wing depressor, was not. SC activation began before wing elevation commenced, with further activation occurring gradually. By contrast, SH activation was swift, starting soon after wing elevation and peaking shortly after the snap. The intensity of this SH activation was comparable to that which occurs during flapping, whereas the SC activation was much lower. Thus, light activation of the SC likely helps position the wings above the back, so that quick, robust SH activation can drive these appendages together to generate the firecracker-like snap sonation. This is one of the first looks at the neuromuscular mechanisms that underlie the actuation of a dynamic courtship display, and it demonstrates that even complex, whole-body display movements can be studied with transmitter-aided EMG techniques.

Seasonal singing of a songbird living near the equator correlates with minimal changes in day length

Behaving in accordance with natural cycles is essential for survival. Birds in the temperate regions use the changes of day length to time their behavior. However, at equatorial latitudes the photoperiod remains almost constant throughout the year, and it is unclear which cues songbirds use to regulate behaviors, such as singing. Here, we investigated the timing of dawn-song of male silver-beaked tanagers in the equatorial lowland Amazonas over two years. In this region, birds experience around nine minutes of annual day length variation, with sunrise times varying by 32 minutes over the year. We show that the seasonal timing of dawn-song was highly regular between years, and was strongly correlated with slight increases in day length. During the singing season the daily dawn-song onset was precisely aligned to variations in twilight time. Thus, although photoperiodic changes near the equator are minimal, songbirds can use day length variation to time singing.

Power-law scaling of calling dynamics in zebra finches

Social mammals and birds have a rich repertoire of communication calls. Some call types are uttered rarely but in specific contexts while others are produced in large numbers but are not linked to a specific context. An example for the latter is the "stack" call that zebra finches (Taeniopygia guttata) utter thousands of times per day in a seemingly erratic manner. We quantified this calling activity of captive zebra finches by using on-bird telemetric microphones that permitted a precise temporal resolution. We separated the calling interactions into the reactive and the self-contained calls. Despite a large dynamic range in the succession of calling events, the temporal distribution of the reactive and the self-contained callings was characterized by a power-law with exponents ranging between 2 and 3, which implies that all calls in that scale have similar dynamic patterns. As birds underwent physiological (water availability) and social (separation from the reproductive partner) changes, their calling dynamics changed. Power-law scaling provided an accurate description of these changes, such that the calling dynamics may inform about an individual's physiological and/or social situations state, even though a single "stack" call has no predetermined meaning.

Drug safety related to agents used for opioid maintenance therapy

Introduction

There is only little data regarding drug safety related to agents used for opioid maintenance therapy (OMT).

Objectives/aims

To study drug safety and the reporting behaviour of adverse drug reactions (ADR) related to OMT.

Methods

A cross-sectional questionnaire-based telephone survey among physicians providing outpatient OMT in a federal state of Germany (n = 176; response rate = 55.7%) was conducted.

Results

Most of the respondents (n = 97/55.1%) reported that they observe ADR related to buprenorphine, [dihydro]codein and [levo]methdone rarely (n = 38/21.6%), very rarely (n = 39/22.2%) or never (n = 20/11.4%). Methadone was reported to be most frequently associated with the occurrence of ADR (n = 82/46.6%), followed by levomethadone (n = 33/18.8%), buprenorphine (n = 6/3.4%), and dihydrocodeine (n = 3/1.7%). Frequently observed ADR related to these agents were gastrointestinal, nervous system and psychiatric disorders, and hyperhidrosis. Methadone and levomethadone (not buprenorphine) were reported to be frequently associated with fatigue, weight gain, and sexual dysfunction. Only buprenorphine was reported to be frequently associated with withdrawal and rebound effects, and drug intolerance. Hundred twenty-nine participants (73.3%) stated that they never report ADR related to OMT, whereas n = 19 (10.8%) did so when referring to ADR related to their complete medical practice (Chi2 = 141.070; df = 1; P < 0.001).

Conclusions

Our data revealed similar patterns of ADR related to outpatient OMT as those reported in the product information or in pain therapy. Motivation to report ADR related to agents used for OMT may be reduced compared to ADR related to the general medical practice.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Web search query data and prescription volumes of antidepressants

Introduction

Persons using the Internet generate large amounts of health-related data, which are increasingly used in modern health sciences.

Objectives/aims

We analysed the relation between annual prescription volumes (APV) of several antidepressants with marketing approval in Germany and corresponding web search query data generated in Google to test, if web search query volume may be a proxy for medical prescription practice.

Methods

We obtained APVs of several antidepressants related to corresponding prescriptions at the expense of the statutory health insurance in Germany from 2004–2013. Web search query data generated in Germany and related to defined search-terms (active substance or brand name) were obtained with Google Trends. We calculated correlations (Pearson's r) between the APVs of each substance and the respective annual “search share” values; coefficients of determination (R2) were computed to determine the amount of variability shared by the two variables.

Results

Significant and strong correlations between substance-specific APVs and corresponding annual query volume were found for each substance during the observational interval: agomelatine (r = 0.968; R2 = 0.932; P = 0.01), bupropion (r = 0.962; R2 = 0.925; P = 0.01), citalopram (r = 0.970; R2 = 0.941; P = 0.01), escitalopram (r = 0.824; R2 = 0.682; P = 0.01), fluoxetine (r = 0.885; R2 = 0.783; P = 0.01), paroxetine (r = 0.801; R2 = 0.641; P = 0.01), and sertraline (r = 0.880; R2 = 0.689; P = 0.01).

Conclusions

Although the used data did not allow to perform an analysis with a higher temporal resolution our results suggest that web search query volume may be a proxy for corresponding prescription behaviour. However, further studies analysing other pharmacologic agents and prescription data that facilitates an increased temporal resolution are needed to confirm this hypothesis.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Absent substance use disorder and survival of extraordinarily high blood alcohol concentration

Introduction

Intoxications with alcohol are very frequent in clinical psychiatry and may lead to death depending on (maximum) blood alcohol concentration (BAC) and accompanying factors as liver function, tolerance, comedication, etc. Death may occur due to ethanol-induced respiratory depression and/or aspiration of gastric content (due to an impaired gag reflex); thus, securing of the airway and ventilation are occasionally necessary.

Objectives/aims

To illustrate the broad range of clinical outcomes of alcohol intoxications and their adequate therapy.

Methods

We present the case of a 58-year female patient with depression who demonstrated a very high BAC of 8.68 g/L (representing the highest survived BAC in literature) due to ingestion of large amounts of alcohol with suicidal intent.

Results

Intubation and ventilation were lifesaving and the patient did not develop any physical or mental consequential damage. As the patient had not regularly used alcohol or any other psychotropic agent tolerance could be ruled out.

Conclusions

This case emphasizes the necessity of rapid securing of the airway in patients with alcohol intoxication and respiratory depression and, furthermore, illustrates the large inter-individual differences regarding ethanol susceptibility.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Hepatotoxicity related to anti-depressive psychopharmacotherapy: Implications of quantitative signal detection

Introduction

Drug-induced liver injury is a major problem of pharmacotherapy and is also frequent with anti-depressive psychopharmacotherapy.

Objectives/aims

However, there are only few studies using a consistent methodologic approach to study hepatotoxicity of a larger group of antidepressants.

Methods

We performed a quantitative signal detection analysis using pharmacovigilance data from the Uppsala monitoring center from the WHO that records adverse drug reaction data from worldwide sources; we calculated reporting odds ratios (ROR) as measures for disproportionality within a case-/non-case approach for several frequently prescribed anti-depressants.

Results

Both positive controls, amineptine (ROR 38.4 [95% CI: 33.8–43.6]) and nefazodone (ROR 3.2 [95% CI: 3.0–3.5]), were statistically associated with hepatotoxicity. Following amineptine, agomelatine (ROR 6.4 [95% CI: 5.7–7.2]) was associated with the second highest ROR, followed by tianeptine (ROR 4.4 [95% CI: 3.6–5.3]), mianserin (ROR 3.6 [95% CI: 3.3–3.4]) and nefazodone.

Conclusions

In line with previous studies our results support the hypothesis that agomelatine and several other anti-depressants may be associated with relevant hepatotoxicity. However, the used data and applied method do not allow a quantitative evaluation of hepatotoxicity or assessment of substance–specific differences regarding the extent of hepatotoxicity.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Comparative Cytogenetics between Two Important Songbird, Models: The Zebra Finch and the Canary

Songbird species (order Passeriformes, suborder Oscines) are important models in various experimental fields spanning behavioural genomics to neurobiology. Although the genomes of some songbird species were sequenced recently, the chromosomal organization of these species is mostly unknown. Here we focused on the two most studied songbird species in neuroscience, the zebra finch (Taeniopygia guttata) and the canary (Serinus canaria). In order to clarify these issues and also to integrate chromosome data with their assembled genomes, we used classical and molecular cytogenetics in both zebra finch and canary to define their chromosomal homology, localization of heterochromatic blocks and distribution of rDNA clusters. We confirmed the same diploid number (2n = 80) in both species, as previously reported. FISH experiments confirmed the occurrence of multiple paracentric and pericentric inversions previously found in other species of Passeriformes, providing a cytogenetic signature for this order, and corroborating data from in silico analyses. Additionally, compared to other Passeriformes, we detected differences in the zebra finch karyotype concerning the morphology of some chromosomes, in the distribution of 5S rDNA clusters, and an inversion in chromosome 1.