Monoaminergic neuronal changes in orexin deficient mice.
ABSTRACT Orexin knockout (KO) mice and orexin/ataxin-3 mice (which have a different pathophysiological background in orexin deficiency) exhibit a phenotype that is similar to human narcolepsy. Although the interactions between the monoaminergic and orexinergic systems are not entirely clear, indirect monoamine-receptor agonists (especially psychostimulants) may contribute to the treatment of narcolepsy. The present study was designed to investigate the interaction between brain orexinergic and monoaminergic neurons as measured by the status of monoaminergic systems and monoamine-related behaviors using orexin-deficient mice. Previous studies have shown that a reduction of monoaminergic tone is related to wakefulness. In the present study, locomotor activity in a novel environment and dopamine turnover was significantly decreased in orexin-deficient mice compared to WT mice, which suggests that psychostimulants may be useful for maintaining wakefulness in orexin deficiency. We also examined the effects of orexin deficiency on psychostimulant-induced hyperlocomotion. The hyperlocomotion induced by methamphetamine and methylphenidate was lower, whereas that induced by MDMA was higher in orexin KO mice compared to WT mice. The sensitivities against psychostimulants in orexin/ataxin-3 mice differed from those in orexin KO mice. These results indicate that the effectiveness of each psychostimulant, which is closely related to its monoaminergic function, was influenced by orexin deficiency itself as well as by the different pathophysiological background in orexin deficiency.
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ABSTRACT: Genetic studies have clearly shown that primary headaches (migraine, tension-type headache and cluster headache) are multifactorial disorders characterized by a complex interaction between different genes and environmental factors. Genetic association studies have highlighted a potential role in the etiopathogenesis of these disorders for several genes related to vascular, neuronal and neuroendocrine functions. A potential role as a therapeutic target is now emerging for some of these genes. The main purpose of this review is to describe new advances in our knowledge regarding the role of MTHFR, KCNK18, TRPV1, TRPV3 and HCRTR genes in primary headache disorders. Involvement of these genes in primary headaches, as well as their potential role in the therapy of these disorders, will be discussed.The Journal of Headache and Pain 07/2013; 14(1):61. DOI:10.1186/1129-2377-14-61 · 3.28 Impact Factor
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ABSTRACT: This study sought to explore the degree of orexin levels in Chinese opiate and methamphetamine addicts and the differences between them. The cross-sectional study was conducted among detoxified drug addicts from Mandatory Detoxification Center (MDC) in five Chinese cities. Orexin levels were assayed with radioimmunoassay (RIA). Mann-Whitney U test and Kruskal-Wallis test were used to detect differences across groups, and logistic regression was used to explore the association between orexin levels and characteristics of demographic and drug abuse. Between November 2009 and January 2011, 285 opiates addicts, 112 methamphetamine addicts, and 79 healthy controls were enrolled. At drug withdrawal period, both opiate and methamphetamine addicts had lower median orexin levels than controls, and median orexin levels in opiate addicts were higher than those in methamphetamine addicts (all above P < 0.05). Adjusted odds of the above median concentration of orexin were higher for injection than "chasing the dragon" (AOR = 3.1, 95% CI = 1.2-7.9). No significant factors associated with orexin levels of methamphetamine addicts were found. Development of intervention method on orexin system by different administration routes especially for injected opiate addicts at detoxification phase may be significant and was welcome.09/2013; 2013:282641. DOI:10.1155/2013/282641
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ABSTRACT: Orexin/hypocretin peptide mutations are rare in humans. Even though human narcolepsy is associated with orexin deficiency, this is only extremely rarely due to mutations in the gene coding prepro-orexin, the precursor for both orexin peptides. In contrast, coding and non-coding variants of the OX1 and OX2 orexin receptors have been identified in many human populations; sometimes, these have been associated with disease phenotype, although most confer a relatively low risk. In most cases, these studies have been based on a candidate gene hypothesis that predicts the involvement of orexins in the relevant pathophysiological processes. In the current review, the known human OX1/HCRTR1 and OX2/HCRTR2 genetic variants/polymorphisms as well as studies concerning their involvement in disorders such as narcolepsy, excessive daytime sleepiness, cluster headache, polydipsia-hyponatremia in schizophrenia, and affective disorders are discussed. In most cases, the functional cellular or pharmacological correlates of orexin variants have not been investigated-with the exception of the possible impact of an amino acid 10 Pro/Ser variant of OX2 on orexin potency-leaving conclusions on the nature of the receptor variant effects speculative. Nevertheless, we present perspectives that could shape the basis for further studies. The pharmacology and other properties of the orexin receptor variants are discussed in the context of GPCR signaling. Since orexinergic therapeutics are emerging, the impact of receptor variants on the affinity or potency of ligands deserves consideration. This perspective (pharmacogenetics) is also discussed in the review.Frontiers in Neuroscience 05/2014; 8:57. DOI:10.3389/fnins.2014.00057