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Elahdadi Salmani M, Sarfi M, Goudarzi I. Hippocampal orexin receptors: Localization and function. VITAMINS AND HORMONES 2022; 118:393-421. [PMID: 35180935 DOI: 10.1016/bs.vh.2021.12.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Orexin (hypocretin) is secreted from the perifornical/lateral hypothalamus and is well known for sleep regulation. Orexin has two, orexin A and B, transcripts and two receptors, type 1 and 2 (OX1R and OX2R), located in the plasma membrane of neurons in different brain areas, including the hippocampus involved in learning, memory, seizures, and epilepsy, as physiologic and pathologic phenomena. OX1R is expressed in the dentate gyrus and CA1 and the OX2R in the CA3 areas. Orexin enhances learning and memory as well as reward, stress, seizures, and epilepsy, partly through OX1Rs, while either aggravating or alleviating those phenomena via OX2Rs. OX1Rs activation induces long-term changes of synaptic responses in the hippocampus, an age and concentration-dependent manner. Briefly, we will review the localization and functions of hippocampal orexin receptors, their role in learning, memory, stress, reward, seizures, epilepsy, and hippocampal synaptic plasticity.
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Affiliation(s)
| | | | - Iran Goudarzi
- School of Biology, Damghan University, Damghan, Iran
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2
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Orexin A peptidergic system: comparative sleep behavior, morphology and population in brains between wild type and Alzheimer’s disease mice. Brain Struct Funct 2022; 227:1051-1065. [PMID: 35066609 PMCID: PMC8930968 DOI: 10.1007/s00429-021-02447-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 12/16/2021] [Indexed: 11/13/2022]
Abstract
Sleep disturbance is common in patients with Alzheimer’s disease (AD), and orexin A is a pivotal neurotransmitter for bidirectionally regulating the amyloid-β (Aβ) deposition of AD brain and poor sleep. In the present study, we examined the characteristic of sleep–wake architecture in APPswe/PSldE9 (APP/PS1) and Aβ-treated mice using electroencephalogram (EEG) and electromyographic (EMG) analysis. We compared the expression of orexin A, distribution, and morphology of the corresponding orexin A-positive neurons using innovative methods including three-dimensional reconstruction and brain tissue clearing between wild type (WT) and APP/PS1 mice. Results from our study demonstrated that increased wakefulness and reduced NREM sleep were seen in APP/PS1 and Aβ treated mice, while the expression of orexin A was significantly upregulated. Higher density and distribution of orexin A-positive neurons were seen in APP/PS1 mice, with a location of 1.06 mm–2.30 mm away from the anterior fontanelle compared to 1.34 mm–2.18 mm away from the anterior fontanelle in WT mice. These results suggested that the population and distribution of orexin A may play an important role in the progression of AD.
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Grafe LA, Geng E, Corbett B, Urban K, Bhatnagar S. Sex- and Stress-Dependent Effects on Dendritic Morphology and Spine Densities in Putative Orexin Neurons. Neuroscience 2019; 418:266-278. [PMID: 31442567 DOI: 10.1016/j.neuroscience.2019.08.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 08/11/2019] [Accepted: 08/13/2019] [Indexed: 01/23/2023]
Abstract
We recently found that non-stressed female rats have higher basal prepro-orexin expression and activation of orexinergic neurons compared to non-stressed males, which lead to impaired habituation to repeated restraint stress at the behavioral, neural, and endocrine level. Here, we extended our study of sex differences in the orexin system by examining spine densities and dendritic morphology in putative orexin neurons in adult male and female rats that were exposed to 5 consecutive days of 30-min restraint. Analysis of spine distribution and density indicated that putative orexinergic neurons in control non-stressed females had significantly more dendritic spines than those in control males, and the majority of these were mushroom spines. This morphological finding may suggest more excitatory input onto orexin neurons in female rats. As orexin neurons are known to promote the hypothalamic-pituitary-adrenal response, this morphological change in orexin neurons could underlie the impaired habituation to repeated stress in female rats. Dendritic complexity did not differ between non-stressed males and females, however repeated restraint stress decreased total dendritic length, nodes, and branching primarily in males. Thus, reduced dendritic complexity of putative orexinergic neurons is observed in males but not in females after 5days of repeated restraint stress. This morphological change might be reflective of decreased orexin system function, which may allow males to habituate more fully to repeated restraint than females. These results extend our understanding of the role of orexin neurons in regulating habituation and demonstrate changes in putative orexin cell morphology and spines that may underlie sex differences in habituation.
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Affiliation(s)
- Laura A Grafe
- Department of Psychology, Bryn Mawr College, Bryn Mawr, PA 19010, USA
| | - Eric Geng
- Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Brian Corbett
- Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Kimberly Urban
- Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Seema Bhatnagar
- Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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Alijanpour S, Khakpai F, Ebrahimi-Ghiri M, Zarrindast MR. Co-administration of the low dose of orexin and nitrergic antagonists induces an antidepressant-like effect in mice. Biomed Pharmacother 2019; 109:589-594. [DOI: 10.1016/j.biopha.2018.10.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 10/02/2018] [Accepted: 10/09/2018] [Indexed: 12/19/2022] Open
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Abstract
The neuropeptides orexins are important in regulating the neurobiological systems that respond to stressful stimuli. Furthermore, orexins are known to play a role many of the phenotypes associated with stress-related mental illness such as changes in cognition, sleep-wake states, and appetite. Interestingly, orexins are altered in stress-related psychiatric disorders such as Major Depressive Disorder and Anxiety Disorders. Thus, orexins may be a potential target for treatment of these disorders. In this review, we will focus on what is known about the role of orexins in acute and repeated stress, in stress-induced phenotypes relevant to psychiatric illness in preclinical models, and in stress-related psychiatric illness in humans. We will also briefly discuss how orexins may contribute to sex differences in the stress response and subsequent phenotypes relevant to mental health, as many stress-related psychiatric disorders are twice as prevalent in women.
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Orexin 2 receptor stimulation enhances resilience, while orexin 2 inhibition promotes susceptibility, to social stress, anxiety and depression. Neuropharmacology 2018; 143:79-94. [PMID: 30240784 DOI: 10.1016/j.neuropharm.2018.09.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Revised: 08/28/2018] [Accepted: 09/11/2018] [Indexed: 02/08/2023]
Abstract
Knockdown of orexin/hypocretin 2 receptor (Orx2) in the basolateral amygdala (BLA) affects anxious and depressive behavior. We use a new behavioral paradigm, the Stress Alternatives Model (SAM), designed to improve translational impact. The SAM induces social stress in adult male mice by aggression from larger mice, allowing for adaptive decision-making regarding escape. In this model, mice remain (Stay) in the oval SAM arena or escape from social aggression (Escape) via routes only large enough for the smaller mouse. We hypothesized intracerebroventricular (icv) stimulation of Orx2 receptors would be anxiolytic and antidepressive in SAM-related social behavior and the Social Interaction/Preference (SIP) test. Conversely, we predicted that icv antagonism of Orx2 receptors would promote anxious and depressive behavior in these same tests. Anxious behaviors such as freezing (both cued and conflict) and startle are exhibited more often in Stay compared with Escape phenotype mice. Time spent attentive to the escape route is more frequent in Escape mice. In Stay mice, stimulation of Orx2 receptors reduces fear conditioning, conflict freezing and startle, and promotes greater attention to the escape hole. This anxiolysis was accompanied by activation of a cluster of inhibitory neurons in the amygdala. A small percentage of those Stay mice also begin escaping; whereas Escape is reversed by the Orx2 antagonist. Escape mice were also Resilient, and Stay mice Susceptible to stress (SIP), with both conditions reversed by Orx2 antagonism or stimulation respectively. Together, these results suggest that the Orx2 receptor may be a useful potential target for anxiolytic or antidepressive therapeutics.
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Enevoldsen LH, Tindborg M, Hovmand NL, Christoffersen C, Ellingsgaard H, Suetta C, Stallknecht BM, Jennum PJ, Kjær A, Gammeltoft S. Functional brown adipose tissue and sympathetic activity after cold exposure in humans with type 1 narcolepsy. Sleep 2018; 41:4996398. [DOI: 10.1093/sleep/zsy092] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Indexed: 11/14/2022] Open
Affiliation(s)
- Lotte Hahn Enevoldsen
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Denmark
| | - Marie Tindborg
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | | | - Christina Christoffersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
- Department of Clinical Biochemistry, Rigshospitalet, Denmark
| | | | - Charlotte Suetta
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Denmark
| | - Bente Merete Stallknecht
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | | | - Andreas Kjær
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Denmark
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
- Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, Denmark
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Barson JR, Leibowitz SF. Orexin/Hypocretin System: Role in Food and Drug Overconsumption. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2017; 136:199-237. [PMID: 29056152 DOI: 10.1016/bs.irn.2017.06.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The neuropeptide orexin/hypocretin (OX), while largely transcribed within the hypothalamus, is released throughout the brain to affect complex behaviors. Primarily through the hypothalamus itself, OX homeostatically regulates adaptive behaviors needed for survival, including food intake, sleep-wake regulation, mating, and maternal behavior. However, through extrahypothalamic limbic brain regions, OX promotes seeking and intake of rewarding substances of abuse, like palatable food, alcohol, nicotine, and cocaine. This neuropeptide, in turn, is stimulated by the intake of or early life exposure to these substances, forming a nonhomeostatic, positive feedback loop. The specific OX receptor involved in these behaviors, whether adaptive behavior or substance seeking and intake, is dependent on the particular brain region that contributes to them. Thus, we propose that, while the primary function of OX is to maintain arousal for the performance of adaptive behaviors, this neuropeptide system is readily co-opted by rewarding substances that involve positive feedback, ultimately promoting their abuse.
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Affiliation(s)
- Jessica R Barson
- Drexel University College of Medicine, Philadelphia, PA, United States
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Rani M, Kumar R, Krishan P. Implicating the potential role of orexin in hypertension. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:667-676. [DOI: 10.1007/s00210-017-1378-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 04/19/2017] [Indexed: 12/12/2022]
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Kuwaki T. Thermoregulation under pressure: a role for orexin neurons. Temperature (Austin) 2015; 2:379-91. [PMID: 27227052 PMCID: PMC4843912 DOI: 10.1080/23328940.2015.1066921] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 06/20/2015] [Accepted: 06/22/2015] [Indexed: 01/06/2023] Open
Abstract
In the past, studies on stress responses and sleep/wake regulation were performed separately. The discovery of orexin (hypocretin) in 1998, however, dramatically changed the course of research and new findings regarding its role in these complex processes provided a better insight into their interactions and intricacies. Orexin-containing neuronal activity has been found to be minimal during sleep. It increases during the waking period and further increases during the active waking period, which includes stress responses and exploratory behaviors. Autonomic regulation of the body, which includes body temperature, blood flow, and ventilation, is also activated along with the change in vigilance states. Our recent findings suggest that orexin neurons act as a conductor of orchestration for vigilance states, behaviors, and autonomic functions. Body temperature regulation by orexin neurons seems to be mediated by one of its cotransmitters while cardiovascular and respiratory regulation are mediated by orexin itself.
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Affiliation(s)
- Tomoyuki Kuwaki
- Department of Physiology; Kagoshima University Graduate School of Medical and Dental Sciences ; Kagoshima, Japan
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Metabolic regulation of lateral hypothalamic glucose-inhibited orexin neurons may influence midbrain reward neurocircuitry. Mol Cell Neurosci 2014; 62:30-41. [PMID: 25107627 DOI: 10.1016/j.mcn.2014.08.001] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/23/2014] [Accepted: 08/02/2014] [Indexed: 12/20/2022] Open
Abstract
Lateral hypothalamic area (LHA) orexin neurons modulate reward-based feeding by activating ventral tegmental area (VTA) dopamine (DA) neurons. We hypothesize that signals of peripheral energy status influence reward-based feeding by modulating the glucose sensitivity of LHA orexin glucose-inhibited (GI) neurons. This hypothesis was tested using electrophysiological recordings of LHA orexin-GI neurons in brain slices from 4 to 6week old male mice whose orexin neurons express green fluorescent protein (GFP) or putative VTA-DA neurons from C57Bl/6 mice. Low glucose directly activated ~60% of LHA orexin-GFP neurons in both whole cell and cell attached recordings. Leptin indirectly reduced and ghrelin directly enhanced the activation of LHA orexin-GI neurons by glucose decreases from 2.5 to 0.1mM by 53±12% (n=16, P<0.001) and 41±24% (n=8, P<0.05), respectively. GABA or neurotensin receptor blockade prevented leptin's effect on glucose sensitivity. Fasting increased activation of LHA orexin-GI neurons by decreased glucose, as would be predicted by these hormonal effects. We also evaluated putative VTA-DA neurons in a novel horizontal slice preparation containing the LHA and VTA. Decreased glucose increased the frequency of spontaneous excitatory post-synaptic currents (sEPSCs; 125 ± 40%, n=9, P<0.05) and action potentials (n=9; P<0.05) in 45% (9/20) of VTA DA neurons. sEPSCs were completely blocked by AMPA and NMDA glutamate receptor antagonists (CNQX 20 μM, n=4; APV 20μM, n=4; respectively), demonstrating that these sEPSCs were mediated by glutamatergic transmission onto VTA DA neurons. Orexin-1 but not 2 receptor antagonism with SB334867 (10μM; n=9) and TCS-OX2-29 (2μM; n=5), respectively, blocks the effects of decreased glucose on VTA DA neurons. Thus, decreased glucose increases orexin-dependent excitatory glutamate neurotransmission onto VTA DA neurons. These data suggest that the glucose sensitivity of LHA orexin-GI neurons links metabolic state and reward-based feeding.
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The action of orexin B on passive avoidance learning. Involvement of neurotransmitters. Behav Brain Res 2014; 272:1-7. [PMID: 24931796 DOI: 10.1016/j.bbr.2014.06.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 06/05/2014] [Accepted: 06/08/2014] [Indexed: 11/22/2022]
Abstract
The extensive projection of orexigenic neurons and the diffuse expression of orexin receptors suggest that endogenous orexins are involved in several physiological functions of the central nervous system, including learning and memory. Our previous study demonstrated that orexin A improves learning, consolidation and retrieval processes, which involves α- and β-adrenergic, cholinergic, dopaminergic, GABA-A-ergic, opiate and nitrergic neurotransmissions. However, we have little evidence about the action of orexin B on memory processes and the underlying neuromodulation. Therefore, the aim of the present study was to investigate the action of orexin B on passive avoidance learning and the involvement of neurotransmitters in this action in rats. Accordingly, rats were pretreated with the selective orexin 2 receptor (OX2R) antagonist, EMPA; the γ-aminobutyric acid subunit A (GABA-A) receptor antagonist, the bicuculline; a D2, D3, D4 dopamine receptor antagonist, haloperidol; the nonselective opioid receptor antagonist, naloxone; the non-specific nitric oxide synthase (NOS) inhibitor, nitro-l-arginine; the nonselective α-adrenergic receptor antagonist, phenoxybenzamine and the β-adrenergic receptor antagonist, propranolol. Our results demonstrate that orexin B can improve learning, consolidation of memory and retrieval. EMPA reversed completely the action of orexin B on memory consolidation. Bicuculline blocked fully; naloxone, nitro-l-arginine, phenoxybenzamine and propranolol attenuated the orexin B-induced memory consolidation, whereas haloperidol was ineffective. These data suggest that orexin B improves memory functions through OX2R and GABA-ergic, opiate, nitrergic, α- and β-adrenergic neurotransmissions are also involved in this action.
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Rainero I, Martino PD, Pinessi L. Hypocretins and primary headaches: neurobiology and clinical implications. Expert Rev Neurother 2014; 8:409-16. [DOI: 10.1586/14737175.8.3.409] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Takahashi Y, Zhang W, Sameshima K, Kuroki C, Matsumoto A, Sunanaga J, Kono Y, Sakurai T, Kanmura Y, Kuwaki T. Orexin neurons are indispensable for prostaglandin E2-induced fever and defence against environmental cooling in mice. J Physiol 2013; 591:5623-43. [PMID: 23959674 DOI: 10.1113/jphysiol.2013.261271] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We recently showed using prepro-orexin knockout (ORX-KO) mice and orexin neuron-ablated (ORX-AB) mice that orexin neurons in the hypothalamus, but not orexin peptides per se, are indispensable for stress-induced thermogenesis. To examine whether orexin neurons are more generally involved in central thermoregulatory mechanisms, we applied other forms of thermogenic perturbations, including brain prostaglandin E2 (PGE2) injections which mimic inflammatory fever and environmental cold exposure, to ORX-KO mice, ORX-AB mice and their wild-type (WT) litter mates. ORX-AB mice, but not ORX-KO mice, exhibited a blunted PGE2-induced fever and intolerance to cold (5°C) exposure, and these findings were similar to the results previously obtained with stress-induced thermogenesis. PGE2-induced shivering was also attenuated in ORX-AB mice. Both mutants responded similarly to environmental heating (39°C). In WT and ORX-KO mice, the administration of PGE2 and cold exposure activated orexin neurons, as revealed by increased levels of expression of c-fos. Injection of retrograde tracer into the medullary raphe nucleus revealed direct and indirect projection from the orexin neurons, of which the latter seemed to be preserved in the ORX-AB mice. In addition, we found that glutamate receptor antagonists (D-(-)-2-amino-5-phosphonopentanoic acid and 6-cyano-7-nitroquinoxaline-2,3-dione) but not orexin receptor antagonists (SB334867 and OX2 29) successfully inhibited PGE2-induced fever in WT mice. These results suggest that orexin neurons are important in general thermogenic processes, and their importance is not restricted to stress-induced thermogenesis. In addition, these results indicate the possible involvement of glutamate in orexin neurons implicated in PGE2-induced fever.
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Affiliation(s)
- Yoshiko Takahashi
- T. Kuwaki: Department of Physiology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka 8-35-1, Kagoshima 890-8544, Japan.
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Xiao F, Jiang M, Du D, Xia C, Wang J, Cao Y, Shen L, Zhu D. Orexin A regulates cardiovascular responses in stress-induced hypertensive rats. Neuropharmacology 2012; 67:16-24. [PMID: 23147417 DOI: 10.1016/j.neuropharm.2012.10.021] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 10/16/2012] [Accepted: 10/20/2012] [Indexed: 01/22/2023]
Abstract
Several pieces of evidence indicate that the rostral ventrolateral medulla (RVLM) is probably one of the key neural structures mediating the pressor effects of orexins in the brain. Nitric oxide synthase/nitric oxide (NOS/NO) system in the RVLM modulates cardiovascular activities. Our experiments were designed to test the hypothesis that orexin-A (OXA) is involved in the mechanism of stress-induced hypertension (SIH) by adjusting NOS/NO system in the RVLM. The stress-induced hypertensive rats (SIHR) model was established by electric foot-shocks and noises. Here we examined the expression of OXA immunoreactive (OXA-IR) cells in the lateral hypothalamus (LH) and the protein level of orexin 1 receptor (OX1R) in the RVLM of SIHR, and we found that the expressions of OXA-IR and OX1R were higher than those of the control group. The double-staining immunohistochemical evidence showed that OX1R immunoreactive (OX1R-IR) cells and neuronal nitric oxide synthase (nNOS) or inducible nitric oxide synthase (iNOS) immunoreactive (IR) cells were co-localizated in the RVLM. Microinjection of OXA (10, 50, 100 pmol/100 nl) into the unilateral (right) RVLM of control rats or SIHR produced pressor and tachycardiac effects in a dose-dependent manner. SB-408124 (100 pmol/100 nl, an antagonist of OX1R) or TCS OX2 29 (100 pmol/100 nl, an antagonist of OX2R) partly abolished the cardiovascular effects of exogenously-administrated OXA into the RVLM of control rats and SIHR, and lowered the increased systolic blood pressure (SBP) and heart rate (HR) of SIHR, with no difference in statistical significance between the two antagonists' effects. Microinjection into the RVLM of both control and SIHR groups of 7-Ni (0.05 pmol/100 nl, nNOS inhibitor) or Methylene Blue [100 pmol/100 nl, an inhibitor of soluble guanylate cyclase (sGC)] suppressed the OXA-induced increase of SBP and HR, whereas microinjection of AG (1, 10, 100 pmol/100 nl) had no obvious effects on the OXA-induced increase of SBP and HR. Our results indicate that OXA in the RVLM may participate in the central regulation of cardiovascular activities in SIHR, and OX1R and OX2R both have important roles in it. The cardiovascular effects of OXA in the RVLM may be induced by nNOS-derived NO, which activated sGC-associated signaling pathway.
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Affiliation(s)
- Fen Xiao
- Department of Physiology and Pathophysiology, Shanghai Medical College of Fudan University, 138 Yixueyuan Road, Shanghai 200032, PR China
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Barson JR, Morganstern I, Leibowitz SF. Neurobiology of consummatory behavior: mechanisms underlying overeating and drug use. ILAR J 2012; 53:35-58. [PMID: 23520598 PMCID: PMC3954603 DOI: 10.1093/ilar.53.1.35] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Consummatory behavior is driven by both caloric and emotional need, and a wide variety of animal models have been useful in research on the systems that drive consumption of food and drugs. Models have included selective breeding for a specific trait, manipulation of gene expression, forced or voluntary exposure to a substance, and identification of biomarkers that predict which animals are prone to overconsuming specific substances. This research has elucidated numerous brain areas and neurochemicals that drive consummatory behavior. Although energy homeostasis is primarily mediated by the hypothalamus, reinforcement is more strongly mediated by nuclei outside the hypothalamus, in mesocorticolimbic regions. Orexigenic neurochemicals that control food intake can provide a general signal for promoting caloric intake or a more specific signal for stimulating consumption of a particular macronutrient, fat, carbohydrate, or protein. The neurochemicals involved in controlling fat ingestion--galanin, enkephalin, orexin, melanin-concentrating hormone, and the endocannabinoids--show positive feedback with this macronutrient, as these peptides both increase fat intake and are further stimulated by its intake. This positive association offers some explanation for why foods high in fat are so often overconsumed. Consumption of ethanol, a drug of abuse that also contains calories, is similarly driven by the neurochemical systems involved in fat intake, according to evidence that closely relates fat and ethanol consumption. Further understanding of the systems involved in consummatory behavior will enable the development of effective therapies for the treatment of both overeating and drug abuse.
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Affiliation(s)
- Jessica R Barson
- Laboratory of Behavioral Neurobiology, The Rockefeller University, New York, New York 10065, USA
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Abstract
Stress increases cardiac function, ventilation, and body temperature and induces analgesia. These changes, which result in an increase in metabolic rate, oxygen supply, and the conduction velocity of nerve impulses, prepare the body for a fight-or-flight response. A part of the hypothalamus called the defense area has long been known to play a key role in these responses, but the precise mechanisms are largely unknown. Our recent findings suggest that orexin (hypocretin) neurons act as a master switch of the fight-or-flight response. In addition, our results, as well as those from other researchers, suggest that orexin neurons do not modulate specific behaviors such as the fight-or-flight responses but rather integrate the autonomic functions and behaviors in a broad sense or in a vigilance state-dependent manner. The orexin system seems to be a pivotal link between the subconscious and the conscious brain functions.
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Affiliation(s)
- Tomoyuki Kuwaki
- Department of Physiology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan
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Kuwaki T. Orexin links emotional stress to autonomic functions. Auton Neurosci 2011; 161:20-7. [DOI: 10.1016/j.autneu.2010.08.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 08/11/2010] [Accepted: 08/11/2010] [Indexed: 01/24/2023]
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Abstract
OBJECTIVES To examine the pattern of distribution and effect of orexin B in the islets of normal and diabetic rats. METHODS Pancreatic tissue fragments collected from normal and diabetic (4 weeks after the onset of diabetes) rats were either processed for immunohistochemistry or treated with different concentrations (10 to 10 mol/L) of orexin B. RESULTS Orexin B-positive nerves were observed in the wall of blood vessels of both normal and diabetic rat pancreas. Orexin B is abundant in the islets of normal rats and colocalized with insulin in β cells. The number of orexin B-positive cells decreased after the onset of diabetes. Orexin B evoked significant (P<0.05) increases in insulin release from the pancreas of normal and diabetic rats. Propranolol, a β-adrenergic receptor antagonist, significantly (P<0.04) reduced the stimulatory effect of orexin B on insulin secretion. Orexin B also induced significant (P<0.05) increases in glucagon release from the pancreas of normal rats but failed to stimulate glucagon secretion from the pancreas of diabetic rats. CONCLUSIONS Orexin B stimulated insulin secretion in normal and diabetic rat pancreas through the β-adrenergic pathway. Orexin B may have an important role in the regulation of islet function.
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Orexin neurons as arousal-associated modulators of central cardiorespiratory regulation. Respir Physiol Neurobiol 2010; 174:43-54. [DOI: 10.1016/j.resp.2010.04.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Revised: 04/15/2010] [Accepted: 04/15/2010] [Indexed: 11/18/2022]
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21
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Zhang W, Sunanaga J, Takahashi Y, Mori T, Sakurai T, Kanmura Y, Kuwaki T. Orexin neurons are indispensable for stress-induced thermogenesis in mice. J Physiol 2010; 588:4117-29. [PMID: 20807795 DOI: 10.1113/jphysiol.2010.195099] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Orexin neurons contribute to cardiovascular, respiratory and analgesic components of the fight-or-flight response against stressors. Here, we examined whether the same is true for stress-induced hyperthermia. We used prepro-orexin knockout mice (ORX-KO) and orexin neuron-ablated mice (ORX-AB) in which the latter lack not only orexin, but also other putative neurotransmitter/modulators contained in the orexin neurons. In response to repetitive insertion of a temperature probe into their rectum (handling stress), ORX-KO mice showed a normal temperature change as compared to that of wild-type littermates (WT) while ORX-AB showed an attenuated response. Stress-induced expression of uncoupling protein-1, a key molecule in non-shivering thermogenesis in the brown adipose tissue (BAT), was also blunted in ORX-AB but not in ORX-KO. When the BAT was directly activated by a β3 adrenergic agonist, there was no difference in the resultant BAT temperature among the groups, indicating that BAT per se was normal in ORX-AB. In WT and ORX-KO, handling stress activated orexin neurons (as revealed by increased expression of c-Fos) and the resultant hyperthermia was largely blunted by pre-treatment with a β3 antagonist. This observation further supports the notion that attenuated stress-induced hyperthermia in ORX-AB mice was caused by a loss of orexin neurons and abnormal BAT regulation. This study pointed out, for the first time, the possible importance of co-existent neurotransmitter/modulators in the orexin neurons for stress-induced hyperthermia and the importance of integrity of the orexin neurons for full expression of multiple facets of the fight-or-flight response.
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Affiliation(s)
- Wei Zhang
- Department of Molecular and Integrative Physiology, Chiba University Graduate School of Medicine, Chiba 260-8670, Japan
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22
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Jeong Y, Holden JE. The role of spinal orexin-1 receptors in posterior hypothalamic modulation of neuropathic pain. Neuroscience 2009; 159:1414-21. [PMID: 19409203 PMCID: PMC3463132 DOI: 10.1016/j.neuroscience.2009.02.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 02/04/2009] [Indexed: 12/24/2022]
Abstract
The posterior hypothalamus (PH) is known to reduce nociceptive pain, but the effect of PH stimulation on neuropathic pain is not known. Because neurons containing the neurotransmitter orexin-A are located in the PH in some strains of rat and intrathecal injection of orexin-A produces antinociception in a neuropathic pain model, we hypothesized that orexin-A from neurons in the PH modifies nociception in the spinal cord dorsal horn. To test this hypothesis, the cholinergic agonist carbachol or normal saline was microinjected into the PH of lightly anesthetized female Sprague-Dawley rats with chronic constriction injury (CCI) and foot withdrawal latencies (FWL) were measured. Carbachol-induced PH stimulation produced dose dependent antinociception as shown by significantly increased FWL compared to saline controls. To investigate the role of orexin-A in PH-induced antinociception, the orexin-1 receptor antagonist SB-334867 or dimethyl sulfoxide (DMSO) for control, was given intrathecally following carbachol-induced PH stimulation. SB-334867 decreased FWL compared to DMSO controls. These data are suggestive that stimulating the PH produces antinociception in a neuropathic pain model and that the antinociceptive effect is mediated in part by orexin-1 receptors in the spinal cord dorsal horn.
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Affiliation(s)
- Younhee Jeong
- Kyunghee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul, 130-701, Korea (ROK), Phone : 82-2-961-2210, Fax : 82-2-961-9398, Email :
| | - Janean E. Holden
- The University of Michigan, 400 N. Ingalls, Room 2340, Ann Arbor, MI 48109-5482, Phone: 734-763-0011, Fax: 734 936-5525,
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23
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Tafuri S, Pavone LM, Mastellone V, Spina A, Avallone L, Vittoria A, Staiano N, Scala G. Expression of orexin A and its receptor 1 in the choroid plexuses from buffalo brain. Neuropeptides 2009; 43:73-80. [PMID: 19250669 DOI: 10.1016/j.npep.2009.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 01/24/2009] [Accepted: 01/24/2009] [Indexed: 10/21/2022]
Abstract
The hypothalamic peptide orexin A, deriving from the proteolytic cleavage of the precursor molecule prepro-orexin, has a wide range of physiological effects including the regulation of feeding behaviour, neuroendocrine functions, sleep-wake cycle, and energy homeostasis. Lowered excretion of orexin A into the cerebrospinal fluid (CSF) plays a pathological role in animal and human narcolepsy. Altered levels of orexin A into the CSF have been also found in numerous disorders of the central nervous system, including Parkinson's and Huntington's disease, dementia, and depressive disorders. While the localization of orexin A and its receptor 1, OX(1), has been elicited in many regions of the mammalian brain and in peripheral organs, there are no information on the expression of the neuropeptide and its receptor 1 in the choroid plexuses (CPs) producing the CSF. In this study, we investigated the expression of orexin A and OX(1) in the CPs from the brain of an adult mammalian species, Bubalis bubalis, by immunogold-labelling in scanning electron microscopy. Both orexin A and OX(1) immuno-reactivity appeared to be widely distributed on the surface of choroid epithelium. Interestingly, a marked orexin A labelling was detected in the areas surrounding the CP blood capillaries. The expression of prepro-orexin and OX(1) mRNA transcripts of 200 and 300 bp, respectively, was assessed in the CPs by reverse-transcription polymerase chain reaction, while Western blotting analysis confirmed the presence of these two proteins in the tissue. Our findings provide the first evidence for orexin A and OX(1) expression in the CPs from mammalian brain, and suggest that the levels of orexin A into the CSF are probably regulated by CP activity.
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Affiliation(s)
- Simona Tafuri
- Department of Biological Structures, Functions and Technologies, University of Naples Federico II, Naples, Italy
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24
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Sarkar S, Zaretskaia MV, Zaretsky DV, Moreno M, DiMicco JA. Stress- and lipopolysaccharide-induced c-fos expression and nNOS in hypothalamic neurons projecting to medullary raphe in rats: a triple immunofluorescent labeling study. Eur J Neurosci 2007; 26:2228-38. [PMID: 17927775 DOI: 10.1111/j.1460-9568.2007.05843.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Neurons in the rostral raphe pallidus (rRP) have been proposed to mediate experimental stress-induced tachycardia and fever in rats, and projections from the dorsomedial hypothalamus (DMH) may signal their activation in these settings. Thus, we examined c-fos expression evoked by air jet/restraint stress and restraint stress or by systemic administration of lipopolysaccharide (10 microg/kg and 100 microg/kg) as well as the distribution of the neuronal nitric oxide synthase (nNOS) in neurons retrogradely labeled from the raphe with cholera toxin B in key hypothalamic regions. Many neurons in the medial preoptic area and the dorsal area of the DMH were retrogradely labeled, and approximately half of those in the medial preoptic area and moderate numbers in the dorsal DMH were also positive for nNOS. Either stress paradigm or dose of lipopolysaccharide increased the number of c-fos-positive neurons and nNOS/c-fos double-labeled neurons in all regions examined. However, retrogradely labeled neurons positive for c-fos were increased only in the dorsal DMH and adjoining region in both stressed and lipopolysaccharide-treated groups, and triple-labeled neurons were found only in this area in rats subjected to either stress paradigm. Thus, hypothalamic neurons that project to the rRP and express c-fos in response to either experimental stress or systemic inflammation are found only in the dorsal DMH, and many of those activated by stress contain nNOS, suggesting that nitric oxide may play a role in signaling in this pathway.
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Affiliation(s)
- Sumit Sarkar
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Dr, Indianapolis, IN 46202, USA
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25
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Riediger T, Giannini P, Erguven E, Lutz T. Nitric oxide directly inhibits ghrelin-activated neurons of the arcuate nucleus. Brain Res 2006; 1125:37-45. [PMID: 17109829 DOI: 10.1016/j.brainres.2006.09.049] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 09/13/2006] [Accepted: 09/15/2006] [Indexed: 01/12/2023]
Abstract
The hypothalamic arcuate nucleus (Arc) is a target site for signals regulating energy homeostasis. The orexigenic hormone ghrelin directly activates neurons of the medial arcuate nucleus (ArcM) in rats. Nitric oxide (NO) is a neuromodulator implicated in the control of food intake and body weight. NO is produced by nitric oxide synthase (NOS) and induces the formation of cyclic guanosine monophosphate (cGMP) via a stimulation of soluble guanylate cyclase (sGC). Both enzymes NOS and sGC have been identified in the Arc. Using extracellular recordings we characterized the effects of NO signaling on ArcM neurons and their co-sensitivity to ghrelin. The artificial NO donor sodium nitroprusside (10(-4) M) reversibly inhibited 91% of all ArcM neurons by a direct postsynaptic mechanism. 52% of ArcM neurons were excited by ghrelin. In all but one of these neurons SNP caused inhibitory responses. The SNP-induced inhibitions were mediated by cGMP since they were blocked by the specific sGC inhibitor ODQ (1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one, 10(-4) M). Furthermore, the membrane permeating cGMP analogue 8-Br-cGMP (10(-4) M) mimicked the inhibitory responses of SNP. In immunohistological in vitro studies SNP induced a cGMP formation, which could also be blocked by ODQ. The current studies demonstrate that NO/cGMP signaling inhibits a large population of ArcM neurons including ghrelin-excited cells. Since an activation of the latter neurons is regarded as a correlate of negative energy balance, NO may represent an anorectic neuromodulator in the Arc and/or restrain the action of signals promoting energy intake. NO signaling in the Arc is also induced following inflammation suggesting a possible role of Arc-intrinsic NO in disease-related anorexia.
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Affiliation(s)
- Thomas Riediger
- Institute of Veterinary Physiology and Center of Integrative Human Physiology, University of Zurich, Winterthurerstr. 260, 8057 Zurich, Switzerland.
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26
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Zhang W, Sakurai T, Fukuda Y, Kuwaki T. Orexin neuron-mediated skeletal muscle vasodilation and shift of baroreflex during defense response in mice. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1654-63. [PMID: 16410401 DOI: 10.1152/ajpregu.00704.2005] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously shown that some features of the defense response, such as increases in arterial blood pressure (AP), heart rate (HR), and ventilation were attenuated in prepro-orexin knockout (ORX-KO) mice. Here, we examined whether the same was true in orexin neuron-ablated [orexin/ataxin-3 transgenic mice (ORX/ATX-Tg)] mice. In addition, we examined other features of the defense response: skeletal muscular vasodilation and shift of baroreceptor reflex. In both anesthetized and conscious conditions, basal AP in ORX/ATX-Tg mice was significantly lower by ∼20 mmHg than in wild-type (WT) controls, as was the case in ORX-KO mice. The difference in AP disappeared after treatment with an α-blocker but not with a β-blocker, indicating lower sympathetic vasoconstrictor outflow. Stimulation of the perifornical area (PFA) in urethane-anesthetized ORX/ATX-Tg mice elicited smaller and shorter-lasting increases in AP, HR, and ventilation, and skeletal muscle vasodilation than in WT controls. In addition, air jet stress-induced elevations of AP and HR were attenuated in conscious ORX/ATX-Tg mice. After pretreatment with a β-blocker, atenolol, stimulation of PFA suppressed phenylephrine (50 μg/kg iv)-induced bradycardia (ΔHR = −360 ± 29 beats/min without PFA stimulation vs. −166 ± 26 during stimulation) in WT. This demonstrated the resetting of the baroreflex. In ORX/ATX-Tg mice, however, no significant suppression was observed (−355 ± 16 without stimulation vs. −300 ± 30 during stimulation). The present study provided further support for our hypothesis that orexin-containing neurons in PFA play a role as a master switch to activate multiple efferent pathways of the defense response and also operate as a regulator of basal AP.
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Affiliation(s)
- Wei Zhang
- Department of Molecular and Integrative Physiology, Chiba University Graduate School of Medicine, 1-8-1 Chuo-ku, Chiba 260-8670, Japan
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27
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Farr SA, Banks WA, Kumar VB, Morley JE. Orexin-A-induced feeding is dependent on nitric oxide. Peptides 2005; 26:759-65. [PMID: 15808906 DOI: 10.1016/j.peptides.2004.12.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2004] [Revised: 12/03/2004] [Accepted: 12/07/2004] [Indexed: 11/24/2022]
Abstract
Orexin-A is a peptide produced in the lateral hypothalamus/perifornical area, which stimulates feeding. The production of orexin-A is determined by the metabolic state of the animal. We have previously shown that nitric oxide (NO) plays an important role as a mediator of feeding induced by a variety of neuropeptides. This raises the question of whether orexin-A's effects are NO dependent. Here, we first determined that intracerebroventricular administration of 25 ng of orexin-A significantly increased food intake in satiated mice. We next examined the effects of Nomega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, on orexin-A-induced increase in food intake. L-NAME (50 mg/kg; SC) significantly blocked the orexin-A-induced increase in food intake. Orexin-A administration increased the levels of nitric oxide synthase in the hypothalamus. To further verify the importance of NO in the orexin-A-induced increase in food intake, we compared the ability of orexin-A to increase food intake in neuronal nitric oxide synthase knockout (NOS-KO) mice and their wild-type controls. Orexin-A failed to increase food intake in the NOS-KO mice, whereas it did increase food intake in the wild-type controls. This supports the hypothesis that nitric oxide is a central regulator of food consumption.
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Affiliation(s)
- Susan A Farr
- Geriatric Research Education and Clinical Center (GRECC), VA Medical Center, and Department of Internal Medicine, Division of Geriatric Medicine, St. Louis University School of Medicine, St. Louis, MO 63106, USA.
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28
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Yao ST, Gouraud S, Paton JFR, Murphy D. Water deprivation increases the expression of neuronal nitric oxide synthase (nNOS) but not orexin-A in the lateral hypothalamic area of the rat. J Comp Neurol 2005; 490:180-93. [PMID: 16052497 DOI: 10.1002/cne.20662] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The discovery that the lateral hypothalamic area (LHA) might be important in modulating drinking behavior and fluid balance has led to numerous studies aimed at identifying the key neurotransmitters/neuromodulators and pathways involved. While past studies have demonstrated the presence of neuronal nitric oxide synthase (nNOS) within the LHA, its role in the regulation of fluid homeostasis is not known. In light of this, and the mounting evidence suggesting a role for nitric oxide in osmotic regulation within the hypothalamus, this study sought to determine the effects of 24- and 72-hours of water deprivation on nNOS protein expression within the LHA of the rat with immunohistochemistry. In euhydrated control animals we observed nNOS-like immunoreactivity throughout all levels of the LHA. Following 24 hours of dehydration the number of nNOS-like immunopositive neurons was significantly increased in the rostral but not the caudal regions of LHA. Seventy-two hours of water deprivation lead to further increases in nNOS-like immunoreactivity at different levels of the LHA. Interestingly, however, we observed increased nNOS-like immunoreactivity in the caudal regions of the LHA that was not evident after 24 hours of water deprivation. Double-labeling immunofluorescence histochemistry revealed that the nNOS-like immunoreactive neurons were not colocalized with the orexin-A-containing neurons. These results suggest that an osmotic challenge leads to an upregulation of nNOS immunoreactivity within discrete areas of the LHA. This altered neurochemistry within the LHA further highlights the potential importance of nitric oxide and the LHA in central regulation of fluid homeostasis.
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Affiliation(s)
- Song T Yao
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK.
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29
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Spina MG, Langnaese K, Orlando GF, Horn TFW, Rivier J, Vale WW, Wolf G, Engelmann M. Colocalization of urocortin and neuronal nitric oxide synthase in the hypothalamus and Edinger-Westphal nucleus of the rat. J Comp Neurol 2004; 479:271-86. [PMID: 15457505 DOI: 10.1002/cne.20318] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Different lines of studies suggest that both the corticotropin-releasing hormone-related peptide Urocortin I (Ucn) and the neuromodulator nitric oxide (NO) are involved in the regulation of the complex mechanisms controlling feeding and anxiety-related behaviors. The aim of the present study was to investigate the possible interaction between Ucn and NO in the hypothalamic paraventricular nucleus (PVN), an area known to be involved in the modulation of these particular behaviors. Therefore, we mapped local mRNA and peptide/protein presence of both Ucn and the NO producing neuronal NO synthase (nNOS). This investigation was extended to include the hypothalamic supraoptic nucleus (SON) and the Edinger-Westphal nucleus area (EW), the latter being one of the major cellular Ucn-expressing sites. Furthermore, we compared the two predominantly used laboratory rat strains, Wistar and Sprague-Dawley. Ucn mRNA and immunoreactivity were detected in the SON and in the EW. A significant difference between Wistar and Sprague-Dawley rats was found in mRNA levels in the EW. nNOS was detected in all brain areas analyzed, showing a significantly lower immunoreactivity in the PVN and EW of Sprague-Dawley versus Wistar rats. Contrary to some previous reports, no Ucn mRNA and only a very low immunoreactivity were detectable in the PVN of either rat strain. Interestingly, double-labeling immunofluorescence revealed that in the SON approximately 75% of all cells immunoreactive for Ucn were colocalized with nNOS, whereas in the EW only approximately 2% of the Ucn neurons were found to contain nNOS. These findings suggest an interaction between Ucn and NO signaling within the SON, rather than the PVN, that may modulate the regulation of feeding, reproduction, and anxiety-related behaviors.
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Affiliation(s)
- Mariarosa G Spina
- Institute of Medical Neurobiology, Otto von Guericke University, Magdeburg D-39120, Germany.
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