Transient targeting of hypothalamic orexin neurons alleviates seizures in a mouse model of epilepsy.

Lateral hypothalamic (LH) hypocretin/orexin neurons (HONs) control brain-wide electrical excitation. Abnormally high excitation produces epileptic seizures, which affect millions of people and need better treatments. HON population activity spikes from minute to minute, but the role of this in seizures is unknown. Here, we describe correlative and causal links between HON activity spikes and seizures. Applying temporally-targeted HON recordings and optogenetic silencing to a male mouse model of acute epilepsy, we found that pre-seizure HON activity predicts and controls the electrophysiology and behavioral pathology of subsequent seizures. No such links were detected for HON activity during seizures. Having thus defined the time window where HONs influence seizures, we targeted it with LH deep brain stimulation (DBS), which inhibited HON population activity, and produced seizure protection. Collectively, these results uncover a feature of brain activity linked to seizures, and demonstrate a proof-of-concept treatment that controls this feature and alleviates epilepsy.

Orexin deficiency affects sensorimotor gating and its amphetamine-induced impairment.

The orexin neuropeptides have an important role in the regulation of the sleep/wake cycle and foraging, as well as in reward processing and emotions. Furthermore, recent research implicates the orexin system in different behavioral endophenotypes of neuropsychiatric diseases such as social avoidance and cognitive flexibility. Utilizing orexin-deficient mice, the present study tested the hypothesis that orexin is involved in two further mouse behavioral endophenotypes of neuropsychiatric disorders, i.e., sensorimotor gating and amphetamine sensitivity. The data revealed that orexin-deficient mice expressed a deficit in sensorimotor gating, measured by prepulse inhibition of the startle response. Amphetamine treatment impaired prepulse inhibition in wildtype and heterozygous orexin-deficient mice, but had no effects in homozygous orexin-deficient mice. Furthermore, locomotor activity and center time in the open field was not affected by orexin deficiency but was similarly increased or decreased, respectively, by amphetamine treatment in all genotypes. These data indicate that the orexin system modulates prepulse inhibition and is involved in mediating amphetamine's effect on prepulse inhibition. Future studies should investigate whether pharmacological manipulations of the orexin system can be used to treat neuropsychiatric diseases associated with deficits in sensorimotor gating, such as schizophrenia or attention deficit hyperactivity disorder.

Electroacupuncture Enhances Neuroplasticity by Regulating the Orexin A-Mediated cAMP/PKA/CREB Signaling Pathway in Senescence-Accelerated Mouse Prone 8 (SAMP8) Mice.

Learning and memory disorders and decreased neuroplasticity are the main clinical manifestations of age-induced cognitive dysfunction. Orexin A (OxA) has been reported to show abnormally elevated expression in the cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and to be associated with cognitive impairment. Here, we further assessed whether the excitatory neurotransmitter OxA is involved in neuroplasticity and cognitive function in senescence-accelerated mouse prone 8 (SAMP8) mice. In this study, we investigated the mechanism of OxA by using behavioral tests, CSF microdialysis, immunofluorescence, toluidine blue staining, gene silencing, transmission electron microscopy, and Western blotting. The results showed that 10 Hz electroacupuncture (EA) effectively alleviated learning and memory impairment in 7-month-old SAMP8 mice, reduced OxA levels in the CSF, increased the level of the neurotransmitter glutamate, alleviated pathological damage to hippocampal tissue, improved the synaptic structure, enhanced synaptic transmission, and regulated the expression of cAMP/PKA/CREB signaling pathway-related proteins. These results suggest that EA enhances neuroplasticity in SAMP8 mice by regulating the OxA-mediated cAMP/PKA/CREB signaling pathway, thus improving cognitive function. These findings suggest that EA may be beneficial for the prevention and treatment of age-induced cognitive impairment.

Zuogui Wan improves trabecular bone microarchitecture in ovariectomy-induced osteoporosis rats by regulating orexin-A and orexin receptor.

OBJECTIVE: To investigate the protective effects of Zuogui Wan (ZGW) on bone loss induced by ovariectomy (OVX) and its mechanism via orexin-A and orexin receptors in the osteoporosis rat model. METHODS: Fifty Sprague-Dawley female rats were randomly divided into sham-operated (sham) group and four OVX subgroups. Rats subjected to sham and OVX were treated with the vehicle (OVX, 1 mL/100 g weight, n = 10), 17ß-estradiol (E2, 50 µg*kg-1*d-1), and ZGW at the doses of 2.3 (ZGW-L) and 4.6 (ZGW-H) g/kg/day lyophilized powder daily for 3 months, respectively. The serum biochemical parameters of 17ß-estrogen (17ß-E2), tartrate-resistant acid phosphatase (TRACP-5b) and bone alkaline phosphatase (BALP) were measured by enzyme-linked immunosorbent assay. Hematoxylin-eosin staining was used to detect the changes in the morphological structure in bones. Microcomputed tomography was used to evaluate the bone mineral density and microarchitecture of the distal femur. The gene or protein expression of orexin-A, orexin receptor 1 (OX1R), orexin receptor 2 (OX2R), osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) were assayed by either quantitative polymerase chain reaction or Western blot analysis. RESULTS: Compared with the OVX group, ZGW could reduce the serum level of TRACP-5b and increased the serum levels of BALP and17ß-E2 (P < 0.01). Meanwhile, ZGW could prevent bone loss and improved bone trabecular microarchitecture by increasing the trabeculae structure thickness and trabecular number, and arranging the trabeculae structure properly. Compared with the OVX group, it was upregulated for the orexin-A and OX2R mRNA or protein expression from the hypothalamus and tibiae, and OPG in the tibiae of ZGW groups (P < 0.01, < 0.05), while downregulated for the OX1R mRNA and protein expression in the tibiae and hypothalamus and RANKL from the tibiae (P < 0.01). CONCLUSION: ZGW exhibited a protective effect for PMOP that may be mediated via orexin-A and orexin receptors regulation.

Hypothalamic kinin B1 receptor mediates orexin system hyperactivity in neurogenic hypertension.

Brain orexin system hyperactivity contributes to neurogenic hypertension. We previously reported upregulated neuronal kinin B1 receptor (B1R) expression in hypertension. However, the role of central B1R activation on the orexin system in neurogenic hypertension has not been examined. We hypothesized that kinin B1R contributes to hypertension via upregulation of brain orexin-arginine vasopressin signaling. We utilized deoxycorticosterone acetate (DOCA)-salt hypertension model in wild-type (WT) and B1R knockout (B1RKO) mice. In WT mice, DOCA-salt-treatment increased gene and protein expression of orexin A, orexin receptor 1, and orexin receptor 2 in the hypothalamic paraventricular nucleus and these effects were attenuated in B1RKO mice. Furthermore, DOCA-salt- treatment increased plasma arginine vasopressin levels in WT mice, but not in B1RKO mice. Cultured primary hypothalamic neurons expressed orexin A and orexin receptor 1. B1R specific agonist (LDABK) stimulation of primary neurons increased B1R protein expression, which was abrogated by B1R selective antagonist R715 but not by the dual orexin receptor antagonist, ACT 462206, suggesting that B1R is upstream of the orexin system. These data provide novel evidence that B1R blockade blunts orexin hyperactivity and constitutes a potential therapeutic target for the treatment of salt-sensitive hypertension.

Impaired hypocretin/orexin system alters responses to salient stimuli in obese male mice.

The brain has evolved in an environment where food sources are scarce, and foraging for food is one of the major challenges for survival of the individual and species. Basic and clinical studies show that obesity or overnutrition leads to overwhelming changes in the brain in animals and humans. However, the exact mechanisms underlying the consequences of excessive energy intake are not well understood. Neurons expressing the neuropeptide hypocretin/orexin (Hcrt) in the lateral/perifonical hypothalamus (LH) are critical for homeostatic regulation, reward seeking, stress response, and cognitive functions. In this study, we examined adaptations in Hcrt cells regulating behavioral responses to salient stimuli in diet-induced obese mice. Our results demonstrated changes in primary cilia, synaptic transmission and plasticity, cellular responses to neurotransmitters necessary for reward seeking, and stress responses in Hcrt neurons from obese mice. Activities of neuronal networks in the LH and hippocampus were impaired as a result of decreased hypocretinergic function. The weakened Hcrt system decreased reward seeking while altering responses to acute stress (stress-coping strategy), which were reversed by selectively activating Hcrt cells with chemogenetics. Taken together, our data suggest that a deficiency in Hcrt signaling may be a common cause of behavioral changes (such as lowered arousal, weakened reward seeking, and altered stress response) in obese animals.

Associations of plasma hypocretin-1 with metabolic and reproductive health: Two systematic reviews of clinical studies.

The hypocretin system consists of two peptides hypocretin-1 and hypocretin-2 (HCRT1 and HCRT2). Hypocretin-containing neurons are located in the posterior and lateral hypothalamus, and have widespread projections throughout the brain and spinal cord. In addition to its presence in the cerebrospinal fluid (CSF), peripheral HCRT1 has been detected in plasma. Robust experimental evidence demonstrates functions of hypothalamic-originated HCRT1 in regulation of multiple biological systems related to sleep-wake states, energy homeostasis and endocrine function. In contrast, HCRT1 studies with human participants are limited by the necessarily invasive assessment of CSF HCRT1 to patients with underlying morbidity. Regulation by HCRT1 of energy homeostasis and reproduction in animals suggests similar regulation in humans and prompts these two systematic reviews. These reviews translate prior experimental findings from animal studies to humans and examine associations between HCRT1 and: 1) metabolic risk factors; 2) reproductive function in men, women and children. A total of 21 studies and six studies met the inclusion criteria for the two searches, respectively. Research question, study design, study population, assessments of HCRT1, reproductive, cardiometabolic data and main findings were extracted. Associations between HCRT1, metabolic and reproductive function are inconsistent. Limitations of studies and future research directions are outlined.

Molecular mechanism of tumour necrosis factor alpha regulates hypocretin (orexin) expression, sleep and behaviour.

Hypocretin 1 and hypocretin 2 (orexin A and B) regulate sleep, wakefulness and emotion. Tumour necrosis factor alpha (TNF-α) is an important neuroinflammation mediator. Here, we examined the effects of TNF-α treatment on hypocretin expression in vivo and behaviour in mice. TNF-α decreased hypocretin 1 and hypocretin 2 expression in a dose-dependent manner in cultured hypothalamic neurons. TNF-α decreased mRNA stability of prepro-hypocretin, the single precursor of hypocretin 1 and hypocretin 2. Mice challenged with TNF-α demonstrated decreased expression of prepro-hypocretin, hypocretin 1 and hypocretin 2 in hypothalamus. In response to TNF-α, prepro-hypocretin mRNA decay was increased in hypothalamus. TNF-α neutralizing antibody restored the expression of prepro-hypocretin, hypocretin 1 and hypocretin 2 in vivo in TNF-α challenged mice, supporting hypocretin system can be impaired by increased TNF-α through decreasing hypocretin expression. Repeated TNF-α challenge induced muscle activity during rapid eye movement sleep and sleep fragmentation, but decreased learning, cognition and memory in mice. TNF-α neutralizing antibody blocked the effects of TNF-α; in contrast, hypocretin receptor antagonist enhanced the effects of TNF-α. The data support that TNF-α is involved in the regulation of hypocretin expression, sleep and cognition. The findings shed some lights on the role of neuroinflammation in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease.

Cafeteria diet induces progressive changes in hypothalamic mechanisms involved in food intake control at different feeding periods in female rats.

We studied the effects of cafeteria diet (CAF) intake from weaning on mRNA levels and DNA methylation state of feeding-related neuropeptides and hormone receptors in individual hypothalamic nuclei at different feeding periods. Four weeks of CAF (short-term) increased energy intake and adiposity, without affecting neuropeptides' expression. Eleven weeks of CAF (medium-term) increased energy intake, adiposity, leptinemia, and body weight, with an orexigenic response of the lateral hypothalamus, paraventricular and ventromedial nuclei, given by upregulation of Orexins, AgRP, and NPY opposed by an anorectic signal of the arcuate nucleus, which displayed a higher POMC expression. The changes in neuropeptidic mRNA levels were related to epigenetic modifications in their promoter regions. Metabolic and molecular changes were intensified after 20 weeks of diet (long-term). The alterations in these hypothalamic brain nuclei could add information about their differential role in food intake control, and how their action is disrupted during the development of obesity.

Considerations related to the use of short neuropeptide promoters in viral vectors targeting hypothalamic neurons.

Targeting specific neuronal cell types is a major challenge for unraveling their function and utilizing specific cells for gene therapy strategies. Viral vector tools are widely used to target specific cells or circuits for these purposes. Here, we use viral vectors with short promoters of neuropeptide genes to target distinct neuronal populations in the hypothalamus of rats and mice. We show that lowering the amount of genomic copies is effective in increasing specificity of a melanin-concentrating hormone promoter. However, since too low titers reduce transduction efficacy, there is an optimal titer for achieving high specificity and sufficient efficacy. Other previously identified neuropeptide promoters as those for oxytocin and orexin require further sequence optimization to increase target specificity. We conclude that promoter-driven viral vectors should be used with caution in order to target cells specifically.

Molecular codes and in vitro generation of hypocretin and melanin concentrating hormone neurons.

Hypocretin/orexin (HCRT) and melanin concentrating hormone (MCH) neuropeptides are exclusively produced by the lateral hypothalamus and play important roles in sleep, metabolism, reward, and motivation. Loss of HCRT (ligands or receptors) causes the sleep disorder narcolepsy with cataplexy in humans and in animal models. How these neuropeptides are produced and involved in diverse functions remain unknown. Here, we developed methods to sort and purify HCRT and MCH neurons from the mouse late embryonic hypothalamus. RNA sequencing revealed key factors of fate determination for HCRT (Peg3, Ahr1, Six6, Nr2f2, and Prrx1) and MCH (Lmx1, Gbx2, and Peg3) neurons. Loss of Peg3 in mice significantly reduces HCRT and MCH cell numbers, while knock-down of a Peg3 ortholog in zebrafish completely abolishes their expression, resulting in a 2-fold increase in sleep amount. We also found that loss of HCRT neurons in Hcrt-ataxin-3 mice results in a specific 50% decrease in another orexigenic neuropeptide, QRFP, that might explain the metabolic syndrome in narcolepsy. The transcriptome results were used to develop protocols for the production of HCRT and MCH neurons from induced pluripotent stem cells and ascorbic acid was found necessary for HCRT and BMP7 for MCH cell differentiation. Our results provide a platform to understand the development and expression of HCRT and MCH and their multiple functions in health and disease.

Effects of Xingnaojing Injection on Adenosinergic Transmission and Orexin Signaling in Lateral Hypothalamus of Ethanol-Induced Coma Rats.

Acute alcohol exposure induces unconscious condition such as coma whose main physical manifestation is the loss of righting reflex (LORR). Xingnaojing Injection (XNJI), which came from Chinese classic formula An Gong Niu Huang Pill, is widely used for consciousness disorders in China, such as coma. Although XNJI efficiently shortened the duration of LORR induced by acute ethanol, it remains unknown how XNJI acts on ethanol-induced coma (EIC). We performed experiments to examine the effects of XNJI on orexin and adenosine (AD) signaling in the lateral hypothalamic area (LHA) in EIC rats. Results showed that XNJI reduced the duration of LORR, which implied that XNJI promotes recovery form coma. Microdialysis data indicated that acute ethanol significantly increased AD release in the LHA but had no effect on orexin A levels. The qPCR results displayed a significant reduction in the Orexin-1 receptors (OX1R) expression with a concomitant increase in the A1 receptor (A1R) and equilibrative nucleoside transporter type 1 (ENT1) expression in EIC rats. In contrast, XNJI reduced the extracellular AD levels but orexin A levels remained unaffected. XNJI also counteracted the downregulation of the OX1R expression and upregulation of A1R and ENT1 expression caused by EIC. As for ADK expression, XNJI but not ethanol, displayed an upregulation in the LHA in EIC rats. Based on these results, we suggest that XNJI promotes arousal by inhibiting adenosine neurotransmission via reducing AD level and the expression of A1R and ENT1.

Involvement of PLAGL1/ZAC1 in hypocretin/orexin transcription.

The hypocretin/orexin neuropeptide system coordinates the regulation of various physiological processes. Our previous study reported that a reduction in the expression of pleomorphic adenoma gene­like 1 (Plagl1), which encodes a C2H2 zinc­finger transcription factor, occurs in hypocretin neuron­ablated transgenic mice, suggesting that PLAGL1 is co­expressed in hypocretin neurons and regulates hypocretin transcription. The present study examined whether canonical prepro­hypocretin transcription is functionally modulated by PLAGL1. Double immunostaining indicated that the majority of hypocretin neurons were positive for PLAGL1 immunoreactivity in the nucleus. Notably, PLAGL1 immunoreactivity in hypocretin neurons was altered in response to several conditions affecting hypocretin function. An uneven localization of PLAGL1 was detected in the nuclei of hypocretin neurons following sleep deprivation. Chromatin immunoprecipitation revealed that endogenous PLAGL1 may bind to a putative PLAGL1­binding site in the proximal region of the hypocretin gene, in the murine hypothalamus. In addition, electroporation of the PLAGL1 expression vector into the fetal hypothalamus promoted hypothalamic hypocretin transcription. These results suggested that PLAGL1 may regulate hypothalamic hypocretin transcription.

Age-related central regulation of orexin and NPY in the short-lived African killifish Nothobranchius furzeri.

Orexin A (OXA) and neuropeptide Y (NPY) are two hypothalamic neuropeptides involved in the regulation of feeding behavior and food intake in all vertebrates. Accumulating evidences document that they undergo age-related modifications, with consequences on metabolism, sleep/wake disorders and progression of neurodegenerations. The present study addressed the age related changes in expression and distribution of orexin A (its precursor is also known as hypocretin-HCRT) and NPY, and their regulation by food intake in the short-lived vertebrate model Nothobranchius furzeri. Our experiments, conducted on male specimens, show that: (a) HCRT and OXA and NPY mRNA and protein are localized in neurons of diencephalon and optic tectum, as well as in numerous fibers projecting through the entire neuroaxis, and are colocalized in specific nuclei; (b) in course of aging, HCRT and NPY expressing neurons are localized also in telencephalon and rhombencephalon; (c) HCRT expressing neurons increased slightly in the diencephalic area of old animals and in fasted animals, whereas NPY increased sharply; (d) central HCRT levels are not regulated neither in course of aging nor by food intake; and (e) central NPY levels are augmented in course of aging, and regulated by food intake only in young. These findings represent a great novelty in the study of central orexinergic and NPY-ergic systems in vertebrates', demonstrating an uncommon and unprecedented described regulation of these two orexigenic neuropeptides.

Activation of orexin system facilitates anesthesia emergence and pain control.

Orexin (also known as hypocretin) neurons in the hypothalamus play an essential role in sleep-wake control, feeding, reward, and energy homeostasis. The likelihood of anesthesia and sleep sharing common pathways notwithstanding, it is important to understand the processes underlying emergence from anesthesia. In this study, we investigated the role of the orexin system in anesthesia emergence, by specifically activating orexin neurons utilizing the designer receptors exclusively activated by designer drugs (DREADD) chemogenetic approach. With injection of adeno-associated virus into the orexin-Cre transgenic mouse brain, we expressed the DREADD receptor hM3Dq specifically in orexin neurons and applied the hM3Dq ligand clozapine to activate orexin neurons. We monitored orexin neuronal activities by c-Fos staining and whole-cell patch-clamp recording and examined the consequence of orexin neuronal activation via EEG recording. Our results revealed that the orexin-DREADD mice with activated orexin neurons emerged from anesthesia with significantly shorter latency than the control mice. As an indication of reduced pain sensitivity, these orexin-DREADD mice took longer to respond to the 55 °C thermal stimuli in the hot plate test and exhibited significantly less frequent licking of the formalin-injected paw in the formalin test. Our study suggests that approaches to activate the orexin system can be beneficial in postoperative recovery.

Melatonin treatment suppresses appetite genes and improves adipose tissue plasticity in diet-induced obese zebrafish.

PURPOSE: Overweight and obesity are important risk factors for diabetes, cardiovascular diseases, and premature death in modern society. Recently, numerous natural and synthetic compounds have been tested in diet-induced obese animal models, to counteract obesity. Melatonin is a circadian hormone, produced by pineal gland and extra-pineal sources, involved in processes which have in common a rhythmic expression. In teleost, it can control energy balance by activating or inhibiting appetite-related peptides. The study aims at testing effects of melatonin administration to control-fed and overfed zebrafish, in terms of expression levels of orexigenic (Ghrelin, orexin, NPY) and anorexigenic (leptin, POMC) genes expression and morphometry of visceral and subcutaneous fat depots. METHODS: Adult male zebrafish (n = 56) were divided into four dietary groups: control, overfed, control + melatonin, overfed + melatonin. The treatment lasted 5 weeks and BMI levels of every fish were measured each week. After this period fishes were sacrificed; morphological and morphometric studies have been carried out on histological sections of adipose tissue and adipocytes. Moreover, whole zebrafish brain and intestine were used for qRT-PCR. RESULTS: Our results demonstrate that melatonin supplementation may have an effect in mobilizing fat stores, in increasing basal metabolism and thus in preventing further excess fat accumulation. Melatonin stimulates the anorexigenic and inhibit the orexigenic signals. CONCLUSIONS: It seems that adequate melatonin treatment exerts anti-obesity protective effects, also in a diet-induced obesity zebrafish model, that might be the result of the restoration of many factors: the final endpoint reached is weight loss and stabilization of weight gain.

Electroacupuncture reduces hypothalamic and medullary expression of orexins and their receptors in a rat model of chronic obstructive pulmonary disease.

OBJECTIVES: Decreased lung function in chronic obstructive pulmonary disease (COPD) is correlated with abnormal excitability of the respiratory centre where orexin neuropeptides from the hypothalamus are responsible for regulating respiration. We hypothesised that improvements in pulmonary function with electroacupuncture (EA) may be related to orexins in a rat model of COPD. METHODS: The COPD model was established by cigarette smoke exposure and lipopolysaccharide injection. Modelled rats received EA at BL13 and ST36 for two weeks, after which lung function was tested. Orexin levels in the hypothalamus and medulla were detected by ELISA, while mRNA/protein expression and localisation of orexins and their receptors were investigated using real time PCR, Western blotting and immunohistochemistry, respectively. RESULTS: The decrease in lung function observed in COPD rats was improved after EA treatment. Orexin levels in the hypothalamus and medulla were significantly higher in COPD rats than in normal rats, but were significantly reduced in the EA-treated group. There was a negative correlation between orexin content and lung function. In the hypothalamus, mRNA and protein expression and immunoreactivity of orexins were significantly higher in the COPD group than in the normal group, but a significant decrease was observed after EA. In the medulla, the expression and immunoreactivity of orexin receptors were significantly higher in the COPD group than in the normal group, but a significant decrease was observed after EA. CONCLUSIONS: The positive effect of EA on pulmonary function in COPD rats may be related to downregulation of orexins and their receptors in the medulla.

DOCA/salt hypertension alters Period1 and orexin-related gene expression in the medulla and hypothalamus of male rats: Diurnal influences.

In peripheral tissues, aldosterone alters expression of multiple genes, including the clock gene Period 1 (Per1), 11 beta-hydroxysteroid dehydrogenase-2 (11-HSD2), and α-ENAC, the epithelial sodium channel subunit. We evaluated the impact of chronic aldosterone exposure (DOCA) and salt intake on nocturnal changes in gene expression in the male Sprague Dawley rat brain. Additionally, genes associated with the orexin (ORX) system were also evaluated based on the role of this neuropeptide in arousal, feeding and hypertension and an interconnection with Per1 expression. DOCA/salt treatment increased saline intake primarily at night, elevated arterial pressure and lowered heart rate. In the medulla oblongata, DOCA/salt upregulated Per1, 11-HSD2, and α-ENAC expression independent of time of day, but did not change ORX receptor type 1 (ORX-R1) or type 2 (ORX-R2) expression. ORX-R1, and ORX-R2 expression in the medulla did however correlate with Per1 expression following DOCA/salt treatment but not in controls. In the hypothalamus, DOCA/salt treatment upregulated Per1, ORX-A, and ORX-R2 expression, in general, and Per1 and ORX-A expression at night. ORX-A, ORX-R1 and ORX-R2 expression in the hypothalamus correlated with Per1 expression following DOCA/salt but not in controls. These findings demonstrate for the first time that DOCA/salt hypertension modulates ORX gene expression in the brain and suggest that changes in expression in the ORX system may occur directly or indirectly via aldosterone-induced changes in Per1 expression. Our findings also build on emerging evidence that monitoring gene expression during both the day and night is critical to understanding the role of specific genes in hypertension.

Accumbal D2 cells orchestrate innate risk-avoidance according to orexin signals.

Excitation of accumbal D2 cells governs vital actions, including avoidance of learned risks, but the origins of this excitation and roles of D2 cells in innate risk-avoidance are unclear. Hypothalamic neurons producing orexins (also called hypocretins) enhance innate risk-avoidance via poorly understood neurocircuits. We describe a direct orexin→D2 excitatory circuit and show that D2 cell activity is necessary for orexin-dependent innate risk-avoidance in mice, thus revealing an unsuspected hypothalamus-accumbens interplay in action selection.