It was recently reported that activation of a subset of lateral hypothalamus (LH) GABAergic neurons induced both appetitive (food-seeking) and consummatory (eating) behaviors in vGat-ires-cre mice, while inhibition or deletion of GABAergic neurons blunted these behaviors. As food and caloric-dense liquid solutions were used, the data reported suggest that these LH GABAergic neurons may modulate behaviors that function to maintain homeostatic caloric balance. Here we report that chemogenetic activation of this GABAergic population in vGat-ires-cre mice increased consummatory behavior directed at any available stimulus, including those entailing calories (food, sucrose, and ethanol), those that do not (saccharin and water), and those lacking biological relevance (wood). Chemogenetic inhibition of these neurons attenuated consummatory behaviors. These data indicate that LH GABAergic neurons modulate consummatory behaviors regardless of the caloric content or biological relevance of the consumed stimuli.

Background Recently, procedures have been developed to model specific facets of human alcohol abuse disorders, including those that model excessive binge-like drinking (i.e., “drinking in the dark”, or DID procedures) and excessive dependence-like drinking (i.e., intermittent ethanol vapor exposure). Similar neuropeptide systems modulate excessive ethanol drinking stemming from both procedures, raising the possibility that both paradigms are actually modeling the same phenotypes and triggering the same central neuroplasticity. Therefore, the goal of the present project was to study the effects of a history of binge-like ethanol drinking, using DID procedures, on phenotypes that have previously been described with procedures to model dependence-like drinking. Methods Male C57BL/6J mice first experienced 0 to 10 4-day binge-like drinking episodes (3 days of rest between episodes). Beginning 24-h after the final binge-like drinking session, mice were tested for anxiety-like behaviors (with elevated plus maze (EPM) and open-field locomotor activity tests), ataxia with the rotarod test, and sensitivity to handling-induced convulsions (HICs). One week later, mice began a 40-day 2-bottle (water versus ethanol) voluntary consumption test with concentration ranging from 10 to 20% (v/v) ethanol. Results A prior history of binge-like ethanol drinking significantly increased subsequent voluntary ethanol consumption and preference, effects most robust in groups that initially experienced 6 or 10 binge-like drinking episodes and completely absent in mice that experienced 1 binge-like drinking episode. Conversely, a history of binge-like ethanol drinking did not influence anxiety-like behaviors, ataxia, or HICs. Conclusions Excessive ethanol drinking stemming from DID procedures does not initially induce phenotypes consistent with a dependence-like state. However, the subsequent increases of voluntary ethanol consumption and preference that become more robust following repeated episodes of binge-like ethanol drinking may reflect the early stages of ethanol dependence, suggesting that DID procedures may be ideal for studying the transition to ethanol dependence.

Background Orexin (OX) neurons originating in the lateral hypothalamus (LH) are ideally positioned to modulate reward processing as they form connections with several key brain regions known to be involved in the reward pathway. Consistent with these findings, a growing number of studies have implicated the OX system in modulating the rewarding properties of several drugs of abuse, including ethanol (EtOH). However, the role of the OX system in excessive binge-like EtOH intake remains relatively unexplored. Here, we assessed changes in OX immunoreactivity (IR) in the hypothalamus following repeated cycles of binge-like EtOH drinking and assessed the participation of the OX-1 receptor (OX1R) in binge-like EtOH consumption. Methods The drinking-in-the-dark (DID) paradigm was used to model binge-like EtOH drinking in male C57BL/6J mice. In the first experiment, mice experienced 1 or 3 cycles of binge-like EtOH or sucrose drinking with DID procedures to assess changes in OX IR in distinct subregions of the hypothalamus. Subsequent experiments examined binge-like EtOH and saccharin drinking following peripheral injections of 0.0, 5.0, or 10.0 mg/kg SB-334867 (SB), a selective OX1R antagonist. Finally, mice were given peripheral injections of SB and open-field locomotor activity was measured. Results Relative to water drinking controls, binge-like consumption of EtOH and sucrose resulted in a marked reduction in OX IR in the LH. Inhibition of the OX1R via SB blunted EtOH and saccharin drinking, but did not alter open-field locomotor activity. Conclusions Our observed reduction in OX IR in the LH indicates that the OX system in engaged during binge-like consumption of EtOH and sucrose. The observation that inhibition of the OX1R signaling blunted binge-like EtOH, and saccharin drinking suggests that reward-related OX circuits originating in the LH participate in the consumption of salient reinforcers regardless of calories.

Affective neuroscience research has revealed that reward contains separable components of 'liking', 'wanting', and learning. Here we focus on current 'liking' and 'wanting' findings and applications to clinical disorders. 'Liking' is the hedonic impact derived from a pleasant experience, and is amplified by opioid and related signals in discrete sites located in limbic-related brain areas. 'Wanting' refers to incentive salience, a motivation process for reward, and is mediated by larger systems involving mesocorticolimbic dopamine. Deficits in incentive salience may contribute to avolitional features of depression and related disorders, whereas deficits in hedonic impact may produce true anhedonia. Excesses in incentive salience, on the other hand, can lead to addiction, especially when narrowly focused on a particular target. Finally, a fearful form of motivational salience may even contribute to some paranoia symptoms of schizophrenia and related disorders.

Background Recent reports have demonstrated that binge-like ethanol drinking leads to an increase in hypothalamic orexin (OX) signaling and that suppressing this signaling via systemic administration of an orexin receptor (OXR) antagonist blocks this behavior; however, the specific OX pathways that modulate this behavior remain unknown. The goal of the present study was to further elucidate the role of the OX system in binge-like ethanol drinking using behavioral, molecular, and pharmacological techniques. Methods The drinking-in-the-dark (DID) paradigm was used to model binge-like drinking behavior in male C57BL/6J mice. Experiment 1 examined changes in the OX precursor, prepro-orexin, within the hypothalamus following multiple cycle ethanol or sucrose DID using polymerase chain reaction (PCR) analysis. In experiments 2a & 2b, we used site-directed infusion of an OXR antagonist to examine the individual contribution of each OXR subtype within the ventral tegmental area (VTA) and central amygdala (CeA), repectively, in binge-like ethanol or sucrose drinking. Results Findings from our PCR study revealed that multiple cycles of binge-like ethanol drinking did not lead to changes in prepro-orexin mRNA as a function of binge-like ethanol drinking. However, data from site-directed pharmacology studies indicate that the OX1R is the predominate receptor subtype within the VTA and CeA that regulates binge-like ethanol drinking. Interestingly, inhibition of OX1Rs did not affect binge-like sucrose intake, which suggests that these OX circuits are specific for ethanol consumption. Conclusions As a whole, these data suggest that the VTA and CeA are important regions in which OX regulates binge-like ethanol drinking behavior. Moreover, these findings identify OXR antagonists as a potential treatment option that may be used to ameliorate problematic drinking behavior while leaving responding to natural rewards relatively intact.