Biology subjects

Jalabert, C.

Publications and source records attributed to Jalabert, C..

3 recordsLinked to original sources

bioRxiv2025

Seasonal plasticity in neuroendocrine mechanisms relevant to year-round territorial aggression in a wild teleost fish

Animals experience cyclical environmental changes, such as seasons, that require physiological adjustments to support different behaviors. Although many behaviors occur only during specific periods, some species, like Gymnotus omarorum, display territorial aggression year-round, making them valuable models to study seasonal plasticity in the mechanisms maintaining stable behavioral outputs. G. omarorum is a teleost fish in which neuroestrogens have been shown to play a key role in non-breeding aggression. Here, we quantified circulating hormone levels and gene expression in the social behavior network of wild breeding and non-breeding individuals. During the non-breeding season, both sexes exhibited elevated circulating androgen levels, providing potential substrates for local estrogen synthesis. Consistently, brain aromatase and estrogen receptor expression were also upregulated, suggesting an increased capacity for local estrogen synthesis and signaling. Our findings provide the first evidence in a teleost of seasonal plasticity in the mechanisms underlying territorial aggression. Comparisons with birds and mammals reveal both shared and lineage-specific strategies, highlighting common endocrine principles while revealing the evolutionary diversity of solutions to maintain a stable behavioral phenotype across changing seasonal contexts.

neuroscience↗

bioRxiv2025

Estrogen profiling in blood and brain: effects of season and an aggressive interaction in a songbird

Neuroestrogens are synthesized in the brain and regulate social behavior and cognition. In the song sparrow (Melospiza melodia), 17{beta}-estradiol (17{beta}-E2) promotes aggression, even during the non-breeding season, when circulating 17{beta}-E2 levels are low. Measuring estrogens is challenging due to their low concentrations and the limited sensitivity of many existing assays. Moreover, estrogens other than 17{beta}-E2 are often overlooked. Here, we developed a method for simultaneous measurement of eleven estrogens that is highly specific, sensitive, accurate, and precise. We used liquid chromatography tandem mass spectrometry (LC-MS/MS) with derivatization of estrogens by 1,2-dimethylimidazole-5-sulfonyl-chloride (DMIS) to enhance sensitivity. We included four 13C-labeled internal standards, which corrected for matrix effects when measuring catecholestrogens and methoxyestrogens. This method greatly improves upon our prior protocol, which could measure only four estrogens and included only one deuterated internal standard. Then, the new method was applied to samples from male song sparrows exposed to either a simulated territorial intrusion (STI) or a control condition during the breeding season or non-breeding season. Only estrone and 17{beta}-E2 were present in blood and brain, while the other nine estrogens in the panel were non-detectable. As expected, there was large regional variation in neuroestrogen levels and very low estrogen levels in blood. There was large seasonal variation, and estrogen levels were lower in the non-breeding season. Despite robust aggressive responses to the STI, estrogen levels did not differ between STI and control subjects in either season. In sum, our novel method enables ultrasensitive measurement of eleven estrogens and will be useful for studies of songbirds and other animals.

neuroscience↗

bioRxiv2023

Brain and circulating steroids in an electric fish: relevance for non-breeding aggression

Steroids play a crucial role in modulating brain and behavior. While traditionally it is considered that the brain is a target of peripheral hormones produced in endocrine glands, it has been discovered that the brain itself produces steroids, known as neurosteroids. Neurosteroids can be produced in brain regions involved in the regulation of social behaviors and can act locally regulating behaviors like reproduction and aggression. Here, for the first time in a teleost fish, we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify a panel of 8 steroids in both plasma and brain. We use the weakly electric fish Gymnotus omarorum, a species which shows non-breeding aggression in both sexes, to characterize these hormonal profiles in wild non-breeding adults. We show that: 1) systemic steroids in the non-breeding season are similar in both sexes, although only males have circulating 11-KT, 2) brain steroid levels are sexually dimorphic, as females display higher levels of AE, T and E1, and only males had 11-KT, 3) systemic androgens such as AE and T in the non-breeding season are potential precursors for neuroestrogen synthesis, and 4) estrogens, which play a key role in non-breeding aggression, are detectable in the brain (but not the plasma) in both sexes. These data fall in line with previous reports in G. omarorum which show that non-breeding aggression is dependent on the estrogenic pathway, as has also been shown in bird and mammal models. Overall, our results constitute a fundamental groundwork to understanding the complexity of hormonal modulation, its potential sex differences, the role of neurosteroids and the interplay between central and peripheral hormones in the regulation of behaviors.

neuroscience↗