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1. Oxytocin neurons signal state-dependent transitions from rest to thermogenesis and behavioral arousal in social and non-social settings

   https://doi.org/10.7554/eLife.108212.2  

   Vandendoren, Morgane; Landen, Jason G; Rogers, Joseph F; Killmer, Samantha; Alamiri, Baizar; Pohlman, Celeste; Tattersall, Glenn J; Bedford, Nicole L; Nelson, Adam C (June 2026, eLife)

   Core body temperature (Tb) is defended within narrow limits through thermoregulatory behaviors like huddling, nesting, and physical activity as well as autonomic responses like brown fat thermogenesis. While Tb displays regulated fluctuations across different behavioral states and rest/arousal cycles, the neural control of these transitions is poorly understood. Here, we investigate the relationship between oxytocin neurons of the paraventricular hypothalamus (PVNOT) and behavioral and autonomic thermoeffector pathways across physiological states in mice. First, we show that PVNOT neurons are activated during social thermoregulation. We then demonstrate that in vivo PVNOT calcium dynamics align with transitions from rest to thermogenesis and behavioral arousal. Counter to our initial hypothesis, these dynamics were observed in both social and non-social contexts. Using a computer vision model to track thermoeffector pathways, we demonstrate that precisely timed stimulation of PVNOT neurons during low-Tb resting states increases thermogenesis followed by behavioral arousal. We therefore suggest a model in which PVNOT neurons facilitate homeostatic state-dependent transitions in thermo-behavioral states. 

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2. Reunion with a peer partner reduces PVN oxytocin neuron immunoreactivity in socially selective voles

   https://doi.org/10.1038/s41598-025-17920-3  

   Goodwin, Nastacia L; Licata, Al M; Power, Kelley C; Reitz, Kara M; Kamal, Yasmin; Beery, Annaliese K (December 2025, Scientific Reports)

   Friendships—i.e. selective peer relationships—are an important aspect of human behavior, but are rare in rodent species. Meadow voles are seasonally social rodents that form non-reproductive social groups in winter/short day lengths that are selective in nature. Across rodents, oxytocin neurons in the paraventricular nucleus (PVN) of the hypothalamus are typically active during socially salient events, including interaction with novel individuals as well as social separation. To assess whether familiar and novel peer interactions produce different patterns of immunolabeling in a species that forms bonds with familiar individuals, we measured oxytocin neuron immunoreactivity and colabeling with the immediate early gene product cFos. Oxytocin labeling and oxytocin/cFos colabeling were higher after interaction with a novel same-sex conspecific than after reunion with a peer partner. Colabeling was also high after 24 h separation without reunion. Circulating corticosterone concentrations paralleled PVN oxytocin neuron activity. We also investigated whether oxytocin signaling was photoperiod dependent and could contribute to seasonal differences in meadow vole social behavior. Oxytocin receptor densities are known to be higher in multiple brain regions in short day lengths in meadow voles, but we found no concomitant change in PVN oxytocin positive cell count. Together these studies indicate that seasonal changes in behavior correlate with oxytocin signaling at the receptor level, while short term experiences modulated oxytocin neuron activity differentially by social context. 

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3. Activation of oxytocinergic neurons enhances torpor in mice

   https://doi.org/10.1007/s00360-023-01528-y  

   Hare, Maia T.; Carter, Matthew E.; Swoap, Steven J. (January 2024, Journal of Comparative Physiology B)

   Mus musculus enters a torpid state in response to caloric restriction in sub-thermoneutral ambient temperatures. This torpid state is characterized by an adaptive and controlled decrease in metabolic rate, heart rate, body temperature, and activity. Previous research has identified the paraventricular nucleus (PVN) within the hypothalamus, a region containing oxytocin neurons, as a location that is active during torpor onset. We hypothesized that oxytocin neurons within the PVN are part of this neural circuit and that activation of oxytocin neurons would deepen and lengthen torpor bouts. We report that activation of oxytocin neurons alone is not sufficient to induce a torpor-like state in the fed mouse, with no significant difference in body temperature or heart rate upon activation of oxytocin neurons. However, we found that activation of oxytocin neurons prior to the onset of daily torpor both deepens and lengthens the subsequent bout, with a 1.7 ± 0.4 °C lower body tempera- ture and a 135 ± 32 min increase in length. We therefore conclude that oxytocin neurons are involved in the neural circuitry controlling daily torpor in the mouse. 

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4. Hypocretin in the nucleus accumbens shell modulates social approach in female but not male California mice

   https://doi.org/10.1038/s41386-024-01937-9  

   Luo, Pei X; Serna_Godoy, Alexandra; Zakharenkov, Hannah Cortez; Vang, Nou; Wright, Emily C; Balantac, Taylor A; Archdeacon, Sinéad C; Black, Alexis M; Lake, Alyssa A; Ramirez, Alison V; et al (December 2024, Neuropsychopharmacology)

   Abstract The hypocretin (Hcrt) system modulates arousal and anxiety-related behaviors and has been considered as a novel treatment target for stress-related affective disorders. We examined the effects of Hcrt acting in the nucleus accumbens shell (NAcSh) and anterodorsal bed nucleus of the stria terminalis (adBNST) on social behavior in male and female California mice (Peromyscus californicus). In female but not male California mice, infusion of Hcrt1 into NAcSh decreased social approach. Weak effects of Hcrt1 on social vigilance were observed in both females and males. No behavioral effects of Hcrt1 infused into the adBNST were observed. Analyses of sequencing data from California mice andMus musculusNAc showed thatHcrtr2was more abundant thanHcrtr1, so we infused the selective Hcrt receptor 2 antagonist into the NAcSh, which increased social approach in females previously exposed to social defeat. A calcium imaging study in the NAcSh of females before and after stress exposure showed that neural activity increased immediately following the expression of social avoidance but not during freezing behavior. This observation is consistent with previous studies that identified populations of neurons in the NAc that drive avoidance. Intriguingly, calcium transients were not affected by stress. These data suggest that hypocretin acting in the NAcSh plays a key role in modulating stress-induced social avoidance. 

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5. The Representation of Affective Internal States in the Hypothalamus: A Neural Manifold View

   https://doi.org/10.1146/annurev-neuro-090225-115629  

   Nair, Aditya; Linderman, Scott; Anderson, David J (July 2026, Annual Review of Neuroscience)

   Our understanding of hypothalamic circuits that control social and other innate survival behaviors has exploded in recent years, thanks to the application of powerful genetically based tools for marking, mapping, manipulating, and monitoring specific neuronal subpopulations. Yet there remains an important set of unanswered questions that must be addressed to fully understand this complex system, including how the hypothalamus encodes affective internal states underlying these behaviors. In systems neuroscience, neural representations of cognitive variables have been revealed by analyzing the activity and dynamics of neural manifolds hidden within high-dimensional population neural activity. These signals are not detectable in the activity of individual neurons or neuron types. Because the hypothalamus has traditionally been viewed as the least “cognitive” part of the brain, the so-called “population doctrine” in cognitive neuroscience has not been widely applied to this system. Here, we discuss recent data that suggest that the application of this manifold-level approach may be useful for identifying representations and mechanisms of internal affective state coding in the hypothalamus. In turn, these findings argue that cognition and emotion may share computational mechanisms to a greater degree than previously assumed. 

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