Neuroendocrine regulation of socially-driven circadian rhythms

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Although social regulation of circadian rhythms is found in a wide variety of animals, we currently lack an understanding of the neuroendocrine mechanisms and the behavioural significance underlying the connection between circadian rhythms and social experience for a socially-relevant behaviour. The long-term objective of my research program is to determine the role of social experience in the neuroendocrine regulation of social behaviours. Due to their electrocommunication signals' tractability and plasticity, the nocturnal gymnotiform electric fish have emerged as an excellent animal model to study the function and the mechanism of social regulation of circadian rhythms. The main objective of the proposed research is to determine the role of the serotonergic system on the regulation of the circadian rhythm of the electric signals of the gymnotiform fish, Brachyhypopomus gauderio. To further characterize the social significance and the mechanisms underlying the relationship between social interactions and electric signal circadian rhythmicity, the proposed research will: 1) clarify the role of the serotonin receptors 1A and 2A in the regulation of the EOD circadian rhythm; 2) determine the social significance of socially-driven changes in the electric signal circadian rhythm; and 3) determine the relationship between the expression of the serotonin receptors 1A and 2A in the central regulatory centers of the hypothalamic-pituitary-adrenal (HPA) axis and hypothalamic neuronal activity. The proposed work is innovative because it: 1) uses the electric signal model as a direct real-time in vivo public broadcast of B. gauderio's neuroendocrine regulatory substrates, and 2) implements an integrative experimental approach that combines pharmacological, molecular, histological and behavioural techniques to describe the role of the serotonergic-HPA pathway on changes in the electric signal's circadian rhythm during social interactions. The results from this project are expected to have an important positive impact because they will advance our knowledge on the mechanisms mediating social influences on the regulation of circadian rhythms, and on the sensitivity of circadian rhythms to different social states.