title: The action of orexin B on passive avoidance learning. Involvement of neurotransmitters.
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.
authors.affiliation: Department of Pathophysiology, Faculty of Medicine, University of Szeged, Szeged, Hungary.
authors.forename: Miklós
authors.initials: M
authors.lastname: Palotai
authors.affiliation: Department of Pathophysiology, Faculty of Medicine, University of Szeged, Szeged, Hungary; MTA-SZTA Neuroscience Research Group of the Hungarian Academy of Sciences, Szeged, Hungary. Electronic address: telegdy.gyula@med.u-szeged.hu.
authors.forename: Gyula
authors.initials: G
authors.lastname: Telegdy
authors.affiliation: Department of Pathophysiology, Faculty of Medicine, University of Szeged, Szeged, Hungary.
authors.forename: Alphonsus
authors.initials: A
authors.lastname: Ekwerike
authors.affiliation: Department of Pathophysiology, Faculty of Medicine, University of Szeged, Szeged, Hungary.
authors.forename: Miklós
authors.initials: M
authors.lastname: Jászberényi
mesh_terms: D018674:Adrenergic Antagonists / Q000494:pharmacology; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009479:Neuropeptides / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000068796:Orexin Receptor Antagonists; D064446:Orexin Receptors / Q000378:metabolism; D000068797:Orexins; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D050637:Receptors, Dopamine D3 / Q000378:metabolism; D050638:Receptors, Dopamine D4 / Q000378:metabolism; D011963:Receptors, GABA-A / Q000378:metabolism; D011957:Receptors, Opioid / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
chemical_list: D018674:Adrenergic Antagonists; D018492:Dopamine Antagonists; D058787:GABA-A Receptor Antagonists; C578625:Hcrtr2 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D009292:Narcotic Antagonists; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D000068796:Orexin Receptor Antagonists; D064446:Orexin Receptors; D000068797:Orexins; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D011963:Receptors, GABA-A; D011957:Receptors, Opioid; D050638:Receptors, Dopamine D4; D019001:Nitric Oxide Synthase
keywords: Neurotransmitter; Orexin B; Passive avoidance learning