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Sleep Sep 2023Long-term use of sodium oxybate (SXB), (also called gamma-hydroxybutyrate [GHB]) attenuates the cataplexy and sleepiness of human narcolepsy. We had previously found...
Long-term use of sodium oxybate (SXB), (also called gamma-hydroxybutyrate [GHB]) attenuates the cataplexy and sleepiness of human narcolepsy. We had previously found that chronic opiate usage in humans and long-term opiate administration to mice significantly increased the number of detected hypocretin/orexin (Hcrt) neurons, decreased their size, and increased Hcrt level in the hypothalamus. We also found that opiates significantly decreased cataplexy in human narcoleptics as well as in narcoleptic mice and that cessation of locus coeruleus neuronal activity preceded and was tightly linked to cataplectic attacks in narcoleptic dogs. We tested the hypothesis that SXB produces changes similar to opiates and now report that chronic SXB administration significantly increased the size of Hcrt neurons, the reverse of what we had seen with opiates in humans and mice. Levels of Hcrt in the hypothalamus were nonsignificantly lower, in contrast to the significant increase in hypothalamic Hcrt level after opiates. SXB decreased tyrosine hydroxylase levels in the locus coeruleus, the major descending projection of the hypocretin system, also the reverse of what we saw with opioids. Therefore despite some similar effects on narcoleptic symptomatology, SXB does not produce anatomical changes similar to those elicited by opiates. Analysis of changes in other links in the cataplexy pathway might further illuminate SXB's mechanism of action on narcolepsy.
Topics: Humans; Mice; Animals; Dogs; Orexins; Sodium Oxybate; Cataplexy; Locus Coeruleus; Narcolepsy; Neurons; Opiate Alkaloids
PubMed: 37155728
DOI: 10.1093/sleep/zsad135 -
Endocrine Reviews Jul 2022The hypocretin/orexin (Hcrt/Orx) system in the perifornical lateral hypothalamus has been recognized as a critical node in a complex network of neuronal systems... (Review)
Review
The hypocretin/orexin (Hcrt/Orx) system in the perifornical lateral hypothalamus has been recognized as a critical node in a complex network of neuronal systems controlling both physiology and behavior in vertebrates. Our understanding of the Hcrt/Orx system and its array of functions and actions has grown exponentially in merely 2 decades. This review will examine the latest progress in discerning the roles played by the Hcrt/Orx system in regulating homeostatic functions and in executing instinctive and learned behaviors. Furthermore, the gaps that currently exist in our knowledge of sex-related differences in this field of study are discussed.
Topics: Animals; Humans; Intracellular Signaling Peptides and Proteins; Neurons; Neuropeptides; Orexins
PubMed: 34792130
DOI: 10.1210/endrev/bnab042 -
Brain Research Bulletin Sep 2023The lateral hypothalamus' orexinergic system has been associated with anxiety-related behaviors, and electroacupuncture (EA) modifies orexin neurons to control the...
The lateral hypothalamus' orexinergic system has been associated with anxiety-related behaviors, and electroacupuncture (EA) modifies orexin neurons to control the anti-anxiety process. However, in a rat model of post-traumatic stress disorder (PTSD), the important role of LH orexin neurons (OXNs) in the anxiolytic effects induced by EA has not been explored. In this study, rats underwent modified single prolonged stress (MSPS) for seven days before developing EA. The rats were then subjected to elevated plus maze (EPM) and open field (OFT) tests, and western blot and c-Fos/orexin double labeling investigations were carried out to determine the functional activation of LH orexinergic neurons. Compared to MSPS model rats, it has been demonstrated that EA stimulation enhanced the amount of time spent in the central zone (TSCZ) in OFT and the amount of time spent in the open arm (TSOA) in EPM in MSPS model rats (P < 0.01). After behavioral testing, MSPS model rats had decreased activated c-Fos positive OXNs. Still, EA in SPS rats increased that number and elevated orexin type 1 receptors (OXR1) protein expression in the LH. Furthermore, after administering SB334867 (an OXR1 antagonist) to MSPS model rats, the effects of EA therapy on anxiety-like behaviors (ALBs) were significantly diminished. Additionally, when low-dose orexin-A (LORXA) was administered intracerebroventricularly together with EA stimulation in MSPS rats, the anxiolytic effects of the stimulation were substantially enhanced (P < 0.05). The results of this study reveal the mechanisms by which acupuncture may reduce PTSD and advance our understanding of the function of LH orexin signaling in EA's anxiolytic effects.
Topics: Animals; Rats; Stress Disorders, Post-Traumatic; Anti-Anxiety Agents; Electroacupuncture; Orexins; Hypothalamic Area, Lateral; Neurons
PubMed: 37481143
DOI: 10.1016/j.brainresbull.2023.110712 -
Frontiers of Neurology and Neuroscience 2021Hypothalamic hypocretin/orexin neurons have been initially conceptualized as slow, modulatory controllers of behavior. Furthermore, their behavioral effects have been... (Review)
Review
Hypothalamic hypocretin/orexin neurons have been initially conceptualized as slow, modulatory controllers of behavior. Furthermore, their behavioral effects have been assumed to be a secondary consequence of their impact on arousal. However, cellular-resolution calcium imaging and optogenetic studies show that orexin neurons regulate self-generated and sensory-evoked movement on rapid, subsecond timescales. Orexin cell activity rapidly and transiently peaks before and during movements. Optogenetic prevention of this activation reduces the probability of locomotion initiation, and optogenetic mimicry of orexin cell activation rapidly causes locomotion. Neural ensemble calcium imaging experiments reveal that the same orexin cells whose activity underlies movement initiation display subsecond-latency responses to diverse sensory stimuli. These findings establish orexin neurons as rapid and strong sensorimotor controllers that are in many ways operationally similar to classic subcortical movement controllers, such as midbrain dopamine neurons. While a scientific definition of "arousal" is still lacking, the subsecond-scale sensorimotor control by orexin neurons could be viewed as reminiscent of a motor rather than an arousal system.
Topics: Animals; Humans; Hypothalamus; Locomotion; Motor Activity; Neurons; Orexins; Sensation
PubMed: 34052808
DOI: 10.1159/000514957 -
Brain Research Mar 2020Orexin has been implicated in a number of physiological functions, including arousal, regulation of sleep, energy metabolism, appetitive behaviors, stress, anxiety,... (Review)
Review
Orexin has been implicated in a number of physiological functions, including arousal, regulation of sleep, energy metabolism, appetitive behaviors, stress, anxiety, fear, panic, and cardiovascular control. In this review, we will highlight research focused on orexin system in the medial hypothalamic regions of perifornical (PeF) and dorsomedial hypothalamus (DMH), and describe the role of this hypothalamic neuropeptide in the behavioral expression of panic and consequent fear and avoidance responses, as well as sympathetic regulation and possible development of chronic hypertension. We will also outline recent data highlighting the clinical potential of single and dual orexin receptor antagonists for neuropsychiatric conditions including panic, phobia, and cardiovascular conditions, such as in hypertension.
Topics: Animals; Brain; Humans; Hypertension; Hypothalamus, Middle; Neural Pathways; Orexin Receptor Antagonists; Orexins; Panic; Phobic Disorders; Stress, Psychological
PubMed: 30205108
DOI: 10.1016/j.brainres.2018.09.010 -
Frontiers of Neurology and Neuroscience 2021Significant sleep impairments often accompany substance use disorders (SUDs). Sleep disturbances in SUD patients are associated with poor clinical outcomes and treatment... (Review)
Review
Significant sleep impairments often accompany substance use disorders (SUDs). Sleep disturbances in SUD patients are associated with poor clinical outcomes and treatment adherence, emphasizing the importance of normalizing sleep when treating SUDs. Orexins (hypocretins) are neuropeptides exclusively produced by neurons in the posterior hypothalamus that regulate various behavioral and physiological processes, including sleep-wakefulness and motivated drug taking. Given its dual role in sleep and addiction, the orexin system represents a promising therapeutic target for treating SUDs and their comorbid sleep deficits. Here, we review the literature on the role of the orexin system in sleep and drug addiction and discuss the therapeutic potential of orexin receptor antagonists for SUDs. We argue that orexin receptor antagonists may be effective therapeutics for treating addiction because they target orexin's regulation of sleep (top-down) and motivation (bottom-up) pathways.
Topics: Animals; Behavior, Addictive; Humans; Motivation; Orexin Receptor Antagonists; Orexins; Reward; Sleep Initiation and Maintenance Disorders; Substance-Related Disorders
PubMed: 34052815
DOI: 10.1159/000514965 -
Philosophical Transactions of the Royal... Apr 2018This article critically reviews evidence relating temperamental traits and personality factors to the monoamine neurotransmitters, especially dopamine and serotonin. The... (Review)
Review
This article critically reviews evidence relating temperamental traits and personality factors to the monoamine neurotransmitters, especially dopamine and serotonin. The genetic evidence is not yet considered to be conclusive and it is argued that basic neuroscience research on the neural basis of behaviour in experimental animals should be taken more into account. While questionnaire and lexical methodology including the 'Five Factor' theory has been informative (mostly for the traits relevant to social functioning, i.e. personality), biologically oriented approaches should be employed with more objective, theoretically grounded measures of cognition and behaviour, combined with neuroimaging and psychopharmacology, where appropriate. This strategy will enable specific functions of monoamines and other neuromodulators such as acetylcholine and neuropeptides (such as orexin) to be defined with respect to their roles in modulating activity in specific neural networks-leading to a more realistic definition of their interactive roles in complex, biologically based traits (i.e. temperament).This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.
Topics: Acetylcholine; Animals; Dopamine; Humans; Individuality; Models, Psychological; Nerve Net; Neuroimaging; Neurotransmitter Agents; Orexins; Psychopharmacology; Psychophysiology; Serotonin; Temperament
PubMed: 29483339
DOI: 10.1098/rstb.2017.0153 -
Nature Neuroscience Oct 2014Orexins (hypocretins) are two peptides (orexin A and B) produced from the pre-pro-orexin precursor and expressed in a limited region of dorsolateral hypothalamus.... (Review)
Review
Orexins (hypocretins) are two peptides (orexin A and B) produced from the pre-pro-orexin precursor and expressed in a limited region of dorsolateral hypothalamus. Orexins were originally thought to specifically mediate feeding and promote wakefulness, but it is now clear that they participate in a wide range of behavioral and physiological processes under select circumstances. Orexins primarily mediate behavior under situations of high motivational relevance, such as during physiological need states, exposure to threats or reward opportunities. We hypothesize that many behavioral functions of orexins (including regulation of sleep/wake cycling) reflect a fundamentally integrated function for orexins in translating motivational activation into organized suites of psychological and physiological processes supporting adaptive behaviors. We also discuss how numerous forms of neural heterogeneity modulate this function, allowing orexin neurons to organize diverse, adaptive responses in a variety of motivationally relevant situations. Thus, the involvement of orexins in diverse behaviors may reflect a common underlying function for this peptide system.
Topics: Animals; Feeding Behavior; Humans; Intracellular Signaling Peptides and Proteins; Models, Biological; Motivation; Neuropeptides; Orexins; Wakefulness
PubMed: 25254979
DOI: 10.1038/nn.3810 -
Current Biology : CB Apr 2023Waking behaviors such as sitting or standing require suitable levels of muscle tone. But it is unclear how arousal and motor circuits communicate with one another so...
Waking behaviors such as sitting or standing require suitable levels of muscle tone. But it is unclear how arousal and motor circuits communicate with one another so that appropriate motor tone occurs during wakefulness. Cataplexy is a peculiar condition in which muscle tone is involuntarily lost during normal periods of wakefulness. Cataplexy therefore provides a unique opportunity for identifying the signaling mechanisms that synchronize motor and arousal behaviors. Cataplexy occurs when hypothalamic orexin neurons are lost in narcolepsy; however, it is unclear if motor-arousal decoupling in cataplexy is directly or indirectly caused by orexin cell loss. Here, we used genomic, proteomic, chemogenetic, electrophysiological, and behavioral assays to determine if grafting orexin cells into the brain of cataplectic (i.e., orexin) mice restores normal motor-arousal behaviors by preventing cataplexy. First, we engineered immortalized orexin cells and found that they not only produce and release orexin but also exhibit a gene profile that mimics native orexin neurons. Second, we show that engineered orexin cells thrive and integrate into host tissue when transplanted into the brain of mice. Next, we found that grafting only 200-300 orexin cells into the dorsal raphe nucleus-a region densely innervated by native orexin neurons-reduces cataplexy. Last, we show that real-time chemogenetic activation of orexin cells restores motor-arousal synchrony by preventing cataplexy. We suggest that orexin signaling is critical for arousal-motor synchrony during wakefulness and that the dorsal raphe plays a pivotal role in coupling arousal and motor behaviors.
Topics: Mice; Animals; Cataplexy; Orexins; Proteomics; Arousal; Wakefulness; Dorsal Raphe Nucleus; Cell Transplantation
PubMed: 37044089
DOI: 10.1016/j.cub.2023.03.077 -
Neuroscience Jun 2020Palatable taste can stimulate appetite in the absence of hunger, and individual differences in hedonic eating may be critical to overeating. Women are more prone to...
Palatable taste can stimulate appetite in the absence of hunger, and individual differences in hedonic eating may be critical to overeating. Women are more prone to obesity and binge eating than men, which warrants comparisons of hedonic versus physiological consumption and the underlying neural substrates in both sexes. The current study examined palatable (high-sugar) food consumption in male and female rats under physiological hunger and satiety, and the role of the neuropeptide orexin/hypocretin (ORX). Across multiple tests, females consistently consumed similar amounts of palatable food regardless of whether they were hungry or sated prior to testing. In contrast, males typically adjusted their consumption according to their hunger/satiety state. This difference was specific to palatable food consumption, as both sexes ate standard chow according to their hunger state. ORX is important in food motivation and reward behaviors. Thus, to begin to determine the neuronal mechanisms of hedonic eating, we examined activation and signaling of ORX neurons. We systematically characterized Fos induction patterns of ORX neurons across the entire rostrocaudal extent of the lateral hypothalamus and found that they were activated by food and by fasting in both sexes. Then, we showed that systemic blockade of ORX receptor 1 signaling with SB-334867 decreased palatable food consumption in hungry and sated rats of both sexes. These results demonstrate sex differences in hedonic eating; increased susceptibility in females to overeat palatable food regardless of hunger state, and that ORX is a critical neuropeptide mechanism of hedonic eating in both sexes.
Topics: Animals; Bulimia; Eating; Female; Hunger; Male; Motivation; Orexins; Rats; Sex Characteristics
PubMed: 32283183
DOI: 10.1016/j.neuroscience.2020.04.008