An appetite for aggressive behavior? Female rats, too, derive reward from winning aggressive interactions

While aggression is an adaptive behavior mostly triggered by competition for resources, it can also in and of itself be rewarding. Based on the common notion that female rats are not aggressive, much of aggression research has been centered around males, leading to a gap in the understanding of the female aggression neurobiology. Therefore, we asked whether intact virgin female rats experience reward from an aggressive interaction and assessed aggression seeking behavior in rats of both sexes. To validate the involvement of reward signaling, we measured mesolimbic dopamine turnover and determined the necessity of dopamine signaling for expression of aggression-seeking. Together our data indicate that female rats exhibit aggressive behavior outside of maternal context, experience winning aggressive behaviors as rewarding, and do so to a similar extent as male rats and in a dopamine-dependent manner

Peripherally restricted oxytocin is sufficient to reduce food intake and motivation, while <scp>CNS</scp> entry is required for locomotor and taste avoidance effects

ObjectivesOxytocin (OT) has a well‐established role in reproductive behaviours; however, it recently emerged as an important regulator of energy homeostasis. In addition to central nervous system (CNS), OT is found in the plasma and OT receptors (OT‐R) are found in peripheral tissues relevant to energy balance regulation. Here, we aim to determine whether peripheral OT‐R activation is sufficient to alter energy intake and expenditure.Methods and ResultsWe first show that systemic OT potently reduced food intake and food‐motivated behaviour for a high‐fat reward in male and female rats. As it is plausible that peripherally, intraperitoneally (IP) injected OT crosses the blood‐brain barrier (BBB) to produce some of the metabolic effects within the CNS, we screened, with a novel fluorescently labelled‐OT (fAF546‐OT, Roxy), for the presence of IP‐injected Roxy in CNS tissue relevant to feeding control and compared such with BBB‐impermeable fluorescent OT‐B$_{12}$ (fCy5‐OT‐B$_{12;}$ BRoxy). While Roxy did penetrate the CNS, BRoxy did not. To evaluate the behavioural and thermoregulatory impact of exclusive activation of peripheral OT‐R, we generated a novel BBB‐impermeable OT (OT‐B$_{12}$), with equipotent binding at OT‐R in vitro. In vivo, IP‐injected OT and OT‐B$_{12}$ were equipotent at food intake suppression in rats of both sexes, suggesting that peripheral OT acts on peripheral OT‐R to reduce feeding behaviour. Importantly, OT induced a potent conditioned taste avoidance, indistinguishable from that induced by LiCl, when applied peripherally. Remarkably, and in contrast to OT, OT‐B$_{12}$ did not induce any conditioned taste avoidance. Limiting the CNS entry of OT also resulted in a dose‐dependent reduction of emesis in male shrews. While both OT and OT‐B$_{12}$ proved to have similar effects on body temperature, only OT resulted in home‐cage locomotor depression.ConclusionsTogether our data indicate that limiting systemic OT CNS penetrance preserves the anorexic effects of the peptide and reduces the clinically undesired side effects of OT: emesis, taste avoidance and locomotor depression. Thus, therapeutic targeting of peripheral OT‐R may be a viable strategy to achieve appetite suppression with better patient outcomes

Elevated circulating adiponectin levels do not prevent anxiety-like behavior in a PCOS-like mouse model

Polycystic ovary syndrome (PCOS) is associated with symptoms of moderate to severe anxiety and depression. Hyperandrogenism is a key feature together with lower levels of the adipocyte hormone adiponectin. Androgen exposure leads to anxiety-like behavior in female offspring while adiponectin is reported to be anxiolytic. Here we test the hypothesis that elevated adiponectin levels protect against the development of androgen-induced anxiety-like behavior. Pregnant mice overexpressing adiponectin (APNtg) and wildtypes were injected with vehicle or dihydrotestosterone to induce prenatal androgenization (PNA) in the offspring. Metabolic profiling and behavioral tests were performed in 4-month-old female offspring. PNA offspring spent more time in the closed arms of the elevated plus maze, indicating anxiety-like behavior. Intriguingly, neither maternal nor offspring adiponectin overexpression prevented an anxiety-like behavior in PNA-exposed offspring. However, adiponectin overexpression in dams had metabolic imprinting effects, shown as lower fat mass and glucose levels in their offspring. While serum adiponectin levels were elevated in APNtg mice, cerebrospinal fluid levels were similar between genotypes. Adiponectin overexpression improved metabolic functions but did not elicit anxiolytic effects in PNA-exposed offspring. These observations might be attributed to increased circulating but unchanged cerebrospinal fluid adiponectin levels in APNtg mice. Thus, increased adiponectin levels in the brain are likely needed to stimulate anxiolytic effects. CC BY 4.0 DEED© 2024, The Author(s)Correspondence Address: A. Benrick; Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Box 423, 40530, Sweden; email: [email protected] access funding provided by University of Gothenburg. AB holds funding from the Swedish Research Council (2020-02485), Magnus Bergvalls Foundation (2022-082), Tore Nilssons Foundation (2022-033), and Hjalmars Svenssons Foundation (2022-291). JPK holds funding from the Swedish Research Council (2021-01549), the Swiss Cancer Research Foundation (KFS-5745-02-2023-R), and Boehringer Ingelheim. ESV holds funding from the Swedish Research Council (2022-00550), the Novo Nordisk Foundation (NNF22OC0072904), KPS is funded by the Swedish Research Council (2018-00660), and the National Institutes of Health R01DK129321, and IWA. holds funding from the Swedish Research Council (2020-01463), Mary von Sydow Foundation (5022), EFSD//European Research Program on ‘New Targets for Diabetes or Obesity-related Metabolic Diseases’ supported by MSD 2022, and Diabetes Wellness Sverige. The funding bodies did not have a role in the study design and had no role in the implementation of the study.</p