title: Orexins excite ventrolateral geniculate nucleus neurons predominantly via OX2 receptors.
abstract: Orexins/hypocretins are two neuropeptides that influence many behaviours, such as feeding, sleep or arousal. Orexin A/hypocretin-1 (OXA) and orexin B/hypocretin-2 (OXB) bind to two metabotropic receptors, named the OX1 and OX2 receptors. The lateral geniculate complex of the thalamus is one of the many targets of orexinergic fibres derived from the lateral hypothalamus, although the impact of orexins on the ventrolateral geniculate nucleus (VLG) is poorly understood. The VLG, an important relay station of the subcortical visual system, is implicated in visuomotor and/or circadian processes. Therefore, in this study we evaluated the effects of orexins on single VLG neurons using a patch-clamp technique in vitro. Surprisingly, orexins depolarised the majority of the recorded neurons regardless of their localisation in the borders of the VLG. In addition, data presented in this article show that neurons synthesising NO were also affected by OXA. Moreover, immunohistochemical staining of OXB revealed the moderate density of orexinergic fibbers in the VLG. Our study using specific orexin receptor antagonists suggests that the OX2 receptor has a dominant role in the observed effects of OXA. To our knowledge, this article is the first to show orexinergic modulation of the VLG. These findings strengthen the postulated link between orexins and the circadian system, and propose a new role of these neuropeptides in the modulation of visuomotor functions.
authors.affiliation: Jagiellonian University, Institute of Zoology, Department of Neurophysiology and Chronobiology, Gronostajowa St. 9, 30-387 Krakow, Poland. Electronic address: lukasz.chrobok@uj.edu.pl.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Chrobok
authors.affiliation: Jagiellonian University, Institute of Zoology, Department of Neurophysiology and Chronobiology, Gronostajowa St. 9, 30-387 Krakow, Poland. Electronic address: benerejka@gmail.com.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Palus
authors.affiliation: Jagiellonian University, Institute of Zoology, Department of Neurophysiology and Chronobiology, Gronostajowa St. 9, 30-387 Krakow, Poland. Electronic address: marian.lewandowski@uj.edu.pl.
authors.forename: Marian Henryk
authors.initials: MH
authors.lastname: Lewandowski
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D005829:Geniculate Bodies / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D000068796:Orexin Receptor Antagonists / Q000494:pharmacology; D064446:Orexin Receptors / Q000502:physiology*; D000068797:Orexins / Q000008:administration & dosage / Q000502:physiology*; D017208:Rats, Wistar
chemical_list: C578625:Hcrtr2 protein, rat; D000068796:Orexin Receptor Antagonists; D064446:Orexin Receptors; D000068797:Orexins
keywords: Immunohistochemistry; In vitro patch-clamp; NADPH-d staining; Orexin; Ventrolateral geniculate nucleus