title: Nucleus incertus Orexin2 receptors mediate alcohol seeking in rats.
abstract: Alcoholism is a chronic relapsing disorder and a major global health problem. Stress is a key precipitant of relapse in human alcoholics and in animal models of alcohol seeking. The brainstem nucleus incertus (NI) contains a population of relaxin-3 neurons that are highly responsive to psychological stressors; and the ascending NI relaxin-3/RXFP3 signalling system is implicated in stress-induced reinstatement of alcohol seeking. The NI receives orexinergic innervation and expresses orexin1 (OX1) and orexin2 (OX2) receptor mRNA. In alcohol-preferring (iP) rats, we examined the impact of yohimbine-induced reinstatement of alcohol seeking on orexin neuronal activation, and the effect of bilateral injections into NI of the OX1 receptor antagonist, SB-334867 (n = 16) or the OX2 receptor antagonist, TCS-OX2-29 (n = 8) on stress-induced reinstatement of alcohol seeking. We also assessed the effects of orexin-A on NI neuronal activity and the involvement of OX1 and OX2 receptors using whole cell patch-clamp recordings in rat brain slices. Yohimbine-induced reinstatement of alcohol seeking activated orexin neurons. Bilateral NI injections of TCS-OX2-29 attenuated yohimbine-induced reinstatement of alcohol seeking. In contrast, intra-NI injection of SB-334867 had no significant effect. In line with these data, orexin-A (600 nM) depolarized a majority of NI neurons recorded in coronal brain slices (18/28 cells), effects prevented by bath application of TCS-OX2-29 (10 μM), but not SB-334867 (10 μM). These data suggest an excitatory orexinergic input to NI contributes to yohimbine-induced reinstatement of alcohol seeking, predominantly via OX2 receptor signalling.
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Hanna E
authors.initials: HE
authors.lastname: Kastman
authors.affiliation: Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Blasiak
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Leigh
authors.initials: L
authors.lastname: Walker
authors.affiliation: Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Siwiec
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Krstew
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Gundlach
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Victoria 3010, Australia. Electronic address: andrew.lawrence@florey.edu.au.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lawrence
mesh_terms: D000818:Animals; D058999:Drug-Seeking Behavior / Q000187:drug effects / Q000502:physiology*; D000431:Ethanol / Q000008:administration & dosage*; D008297:Male; D008845:Microinjections; D000068796:Orexin Receptor Antagonists / Q000008:administration & dosage*; D064446:Orexin Receptors / Q000502:physiology*; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012646:Self Administration; D015016:Yohimbine / Q000008:administration & dosage
chemical_list: D000068796:Orexin Receptor Antagonists; D064446:Orexin Receptors; D015016:Yohimbine; D000431:Ethanol
keywords: Alcohol; Nucleus incertus; Orexin; Reinstatement; Relaxin-3; Stress