Browsing by Author "Teles, Magda"
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- Adult neurogenesis in a new model specie, the cichlid fish Oreochromis mossambicusPublication . Teles, Magda; Oliveira, Rui FilipeEm comparação com outros vertebrados, os peixes teleósteos têm um enorme potencial para produzir células novas no cérebro de animais adultos. Em contraste com os mamíferos, onde o processo de neurogénese adulta encontra-se restrito a duas áreas cerebrais, a zona subventricular (SVZ) e a zona subgranular parte do giro dentado do hipocampo, em peixes teleósteos foram descritas mais de 10 regiões neurogénicas. Através da marcação de células mitóticas com 5-bromo-2’-deoxiuridina (BrdU), foram caracterizadas as zonas proliferativas da Tilapia de Moçambique (Oreochromis mossanbicus). Nesta espécies, foram encontradas zonas proliferativas em regiões específicas do bolbos olfactivo, telecéfalo, região pré-optica, hipotálamo, tálamo, tecto óptico, torus longitudinalis, nas três divisões do cerebelo, valvula cerebelli, corpus cerebelli, e lobus caudalis e na região da medula, abrangendo assim toda a extensão cerebral. A localização destas zonas proliferativas parece ser extremamente conservada ao longo da taxonomia e até o número total de células produzidas parece ser mantido com pouca variação. Com um tempo de sobrevivência de 2 horas, foram encontrados na tilapia um total de 80.000 células novas em comparação com as 100.000 descritas para o peixe eléctrico Apteronotus leptorhynchus. Os nossos resultados sugerem que a actividade mitótica em regiões discretas do cérebro adulto são uma característica primitiva que tem sido conservada ao longo da evolução.
- Agonistic interactions elicit rapid changes in brain nonapeptide levels in zebrafishPublication . Teles, Magda; Gozdowska, Magdalena; Kalamarz-Kubiak, Hanna; Kulczykowska, Ewa; Oliveira, Rui FilipeThe teleost fish nonapeptides, arginine vasotocin (AVT) and isotocin (IT), have been implicated in the regulation of social behavior. These peptides are expected to be involved in acute and transient changes in social context, in order to be efficient in modulating the expression of social behavior according to changes in the social environment. Here we tested the hypothesis that short-term social interactions are related to changes in the level of both nonapeptides across different brain regions. For this purpose we exposed male zebrafish to two types of social interactions: (1) real opponent interactions, from which a Winner and a Loser emerged; and (2) mirror-elicited interactions, that produced individuals that did not experience a change in social status despite expressing similar levels of aggressive behavior to those of participants in real-opponent fights. Non-interacting individuals were used as a reference group. Each social phenotype (i.e. Winners, Losers, Mirror-fighters) presented a specific brain profile of nonapeptides when compared to the reference group. Moreover, the comparison between the different social phenotypes allowed to address the specific aspects of the interaction (e.g. assessment of opponent aggressive behavior vs. self-assessment of expressed aggressive behavior) that are linked with neuropeptide responses. Overall, agonistic interactions seem to be more associated with the changes in brain AVT than IT, which highlights the preferential role of AVT in the regulation of aggressive behavior already described for other species.
- Androgen response to social competition in a shoaling fishPublication . Teles, Magda; Oliveira, Rui FilipeAndrogens respond to social challenges and this response has been interpreted as a way for males to adjust androgen-dependent behavior to social context. However, the androgen responsiveness to social challenges varies across species and a conceptual framework has been developed to explain this variation according to differences in the mating system and parental care type, which determines the regimen of challenges males are exposed to, and concomitantly the scope (defined as the difference between the physiological maximum and the baseline levels) of response to a social challenge. However, this framework has been focused on territorial species and no clear predictions have been made to gregarious species (e.g. shoaling fish), which although tolerating same-sex individuals may also exhibit intra-sexual competition. In this paper we extend the scope of this conceptual framework to shoaling fish by studying the endocrine response of zebrafish (Danio rerio) to social challenges. Male zebrafish exposed to real opponent agonistic interactions exhibited an increase in androgen levels (11-ketotestosterone both in Winners and Losers and testosterone in Losers). This response was absent in Mirror-fighters, that expressed similar levels of aggressive behavior to those of winners, suggesting that this response is not a mere reflex of heightened aggressive motivation. Cortisol levels were also measured and indicated an activation of the hypothalamic-pituitary-interrenal axis in Winners of real opponent fighters, but not Losers or in Mirror-fighters. These results confirm that gregarious species also exhibit an endocrine response to an acute social challenge.
- Assessment of fight outcome is needed to activate socially driven transcriptional changes in the zebrafish brainPublication . Oliveira, Rui Filipe; Simões, José Miguel; Teles, Magda; Oliveira, Catarina R.; Becker, Jorg D.; Lopes, João SollariGroup living animals must be able to express different behavior profiles depending on their social status. Therefore, the same genotype may translate into different behavioral phenotypes through socially driven differential gene expression. However, how social information is translated into a neurogenomic response and what are the specific cues in a social interaction that signal a change in social status are questions that have remained unanswered. Here, we show for the first time, to our knowledge, that the switch between status-specific neurogenomic states relies on the assessment of fight outcome rather than just on self- or opponent-only assessment of fighting ability. For this purpose, we manipulated the perception of fight outcome in male zebrafish and measured its impact on the brain transcriptome using a zebrafish whole genome gene chip. Males fought either a real opponent, and a winner and a loser were identified, or their own image on a mirror, in which case, despite expressing aggressive behavior, males did not experience either a victory or a defeat. Massive changes in the brain transcriptome were observed in real opponent fighters, with losers displaying both a higher number of differentially expressed genes and of coexpressed gene modules than winners. In contrast, mirror fighters expressed a neurogenomic state similar to that of noninteracting fish. The genes that responded to fight outcome included immediate early genes and genes involved in neuroplasticity and epigenetic modifications. These results indicate that, even in cognitively simple organisms such as zebrafish, neurogenomic responses underlying changes in social status rely on mutual assessment of fighting ability.
- Brain and gonadal aromatase activity and steroid hormone levels in female and polymorphic males of the peacock blenny Salaria pavoPublication . Gonçalves, David; Teles, Magda; Alpedrinha, João; Oliveira, Rui FilipeIn the peacock blenny Salaria pavo large males with well-developed secondary sexual characters establish nests and attract females while small “sneaker” males mimic female sexual displays in order to approach the nests of larger males and parasitically fertilize eggs. These alternative reproductive tactics are sequential, as sneakers irreversibly switch into nesting males. This transition involves major morphologic and behavioral changes and is likely to be mediated by hormones. This study focuses on the role of aromatase, an enzyme that catalyses the conversion of androgens into estrogens, in the regulation of male sexual polymorphism in S. pavo. For this, sex steroid plasma levels and aromatase activity (AA) in gonads, whole brain and brain macroareas were determined in sneakers, transitional males (i.e. sneakers undergoing the transition into nesting males), nesting males and females collected in the field. AAwas much higher in ovarian tissue than in testicular tissue and accordingly circulating estradiol levels were highest in females. This supports the view that elevated AA and estradiol levels are associated with the development of a functional ovary. Transitional males are in a non-reproductive phase and had underdeveloped testes when compared with sneakers and nesting males. Testicular AA was approximately 10 times higher in transitional males when compared with sneakers and nesting males, suggesting high AA has a suppressive effect on testicular development. Nesting males had significantly higher plasma levels of both testosterone (T) and 11-ketotestosterone when compared with the other male morphs and previous studies demonstrated that these androgens suppress female-like displays in sneakers. In the brain, AA was highest in macroareas presumably containing hypothalamic nuclei traditionally associated with the regulation of reproductive behaviors. Overall, females presented the highest levels of brain AA. In male morphs AA increased from sneakers, to transitional males, to nesting males in all brain macroareas. These results suggest that the transition into the nesting male tactic is accompanied both by an increase in testicular androgen production and by a higher conversion of androgens into estrogens in the brain. The increase in androgen production is likely to mediate the development of male secondary sexual characters while the increase in brain AA may be related to the behavioral changes associated with tactic transition.
- Brain aromatase mRNA expression in two populations of the peacock blenny Salaria pavo with divergent mating systemsPublication . Gonçalves, David; Saraiva, João Luis Vargas de Almeida; Teles, Magda; Teodósio, Rita; Canário, Adelino V. M.; Oliveira, Rui FilipeAromatase, the key enzyme in the conversion of androgens to estrogens, regulates the availability of these hormones in tissues and controls many physiological and behavioral processes. In fish and other vertebrates, the regulation of aromatase expression in the brain has been implicated in the modulation of male sexual and aggressive behaviors. Here, the pattern of mRNA expression of the brain aromatase isoform (encoded by the CYP19A2 gene also referred as CYP19b) was quantified at the peak of spawning season in brain macroareas from males and females of the blenny Salaria pavo originated from two populations displaying male alternative reproductive tactics but differing in their mating systems. In Trieste (Adriatic) nesting males aggressively defend nests and take the initiative in courtship and perform sexual displays more often than females while in Ria Formosa (Southern Portugal) the pattern is reversed as a result of shortage of appropriate nesting sites. Nesting males from Ria Formosa had overall higher levels of brain aromatase mRNA expression than nesting males from Trieste, suggesting a higher brain estrogen synthesis in these males. Since in some fish species exogenous estradiol administration has been shown to decrease sexual and agonistic behaviors, the higher levels of brain aromatase in Ria Formosa nesting males may explain their reduced expression of sexual and aggressive displays when compared with nesting males from Trieste. Alternatively, the higher brain aromatase levels in nesting males from Ria Formosa could be a mechanism to decrease the putative androgen-induced activation of aggressive and sexual displays by reducing the local availability of androgens through their metabolization into estrogens. Although females and parasitic female-like males also differ in their displays between populations, the interpopulational pattern of brain aromatase mRNA expression was similar, suggesting that other neuroendocrine agents mediate the expression of female and female-like behaviors. In conclusion, brain aromatase availability seems like a probable mechanism to regulate the effects of steroids on the brain circuits underlying the expression of sexual and agonistic displays in S. pavo.
- Endocrine control of sexual behavior in sneaker males of the peacock blenny Salaria pavo: Effects of castration, aromatase inhibition, testosterone and estradiolPublication . Gonçalves, David; Alpedrinha, João; Teles, Magda; Oliveira, Rui FilipeThe effects of castration and sex steroid manipulations on the expression of sexual behavior were investigated in a small fish, the peacock blenny, Salaria pavo. In this species, large males defend nests and attract females while small “sneaker” males reproduce by imitating the female morphology and courtship behavior in order to approach nests during spawning events and parasitically fertilize eggs. Sneakers switch into nest holders in their second breeding season, thus displaying both male and female-like sexual behavior during their lifetime. We tested the effects of castration and of an aromatase inhibitor (Fadrozole, F), testosterone (T) or 17β-estradiol (E2) implants on the expression of male and female-like behavior in sneakers. Sneakers were either sham-operated, castrated or castrated and implanted with vehicle, F, T+F or E2+F. Seven days after the treatment, sneakers were placed in a tank with a nesting male, two ripe females and an available nest. Castrated fish had lower levels of circulating T and increased the time spent displaying female typical nuptial coloration. T implants had the opposite effect, inhibiting the expression of femalelike behavior and coloration. E2 implants had no significant effect on the display of sexual behavior but the frequency of aggressive displays decreased. The results agree with previous findings in sneakers of S. pavo that demonstrated an inhibition of female-like behavior by 11- ketotestosterone (11-KT). The reported increase in T and 11-KT production when sneakers change into nest holders may thus contribute to behaviorally defeminize sneakers. Contrarily, both T and E2 failed to promote male-like behavior, suggesting that behavioral masculization during tactic switching depends on other neuroendocrine mechanisms or that the time length of the experiment was insufficient to induce male-like behavioral changes in sneakers.
- Neurogenomic mechanisms of social plasticityPublication . Cardoso, Sara D.; Teles, Magda; Oliveira, Rui FilipeGroup-living animals must adjust the expression of their social behaviour to changes in their social environment and to transitions between life-history stages, and this social plasticity can be seen as an adaptive trait that can be under positive selection when changes in the environment outpace the rate of genetic evolutionary change. Here, we propose a conceptual framework for understanding the neuromolecular mechanisms of social plasticity. According to this framework, social plasticity is achieved by rewiring or by biochemically switching nodes of a neural network underlying social behaviour in response to perceived social information. Therefore, at the molecular level, it depends on the social regulation of gene expression, so that different genomic and epigenetic states of this brain network correspond to different behavioural states, and the switches between states are orchestrated by signalling pathways that interface the social environment and the genotype. Different types of social plasticity can be recognized based on the observed patterns of inter- versus intra-individual occurrence, time scale and reversibility. It is proposed that these different types of social plasticity rely on different proximate mechanisms at the physiological, neural and genomic level.
- Quantifying aggressive behavior in zebrafishPublication . Teles, Magda; Oliveira, Rui FilipeAggression is a complex behavior that influences social relationships and can be seen as adaptive or maladaptive depending on the context and intensity of expression. A model organism suitable for genetic dissection of the underlying neural mechanisms of aggressive behavior is still needed. Zebrafish has already proven to be a powerful vertebrate model organism for the study of normal and pathological brain function. Despite the fact that zebrafish is a gregarious species that forms shoals, when allowed to interact in pairs, both males and females express aggressive behavior and establish dominance hierarchies. Here, we describe two protocols that can be used to quantify aggressive behavior in zebrafish, using two different paradigms: (1) staged fights between real opponents and (2) mirror-elicited fights. We also discuss the methodology for the behavior analysis, the expected results for both paradigms, and the advantages and disadvantages of each paradigm in face of the specific goals of the study.
- Social interactions elicit rapid shifts in functional connectivity in the social decision-making network of zebrafishPublication . Teles, Magda; Almeida, Olinda; Lopes, João Sollari; Oliveira, Rui FilipeAccording to the social decision-making (SDM) network hypothesis, SDM is encoded in a network of forebrain and midbrain structures in a distributed and dynamic fashion, such that the expression of a given social behaviour is better reflected by the overall profile of activation across the different loci rather than by the activity of a single node. This proposal has the implicit assumption that SDM relies on integration across brain regions, rather than on regional specialization. Here we tested the occurrence of functional localization and of functional connectivity in the SDM network. For this purpose we used zebrafish to map different social behaviour states into patterns of neuronal activity, as indicated by the expression of the immediate early genes c-fos and egr-1, across the SDM network. The results did not support functional localization, as some loci had similar patterns of activity associated with different social behaviour states, and showed socially driven changes in functional connectivity. Thus, this study provides functional support to the SDM network hypothesis and suggests that the neural context in which a given node of the network is operating (i.e. the state of its interconnected areas) is central to its functional relevance.