title: Reduced brown adipose tissue thermogenesis during environmental interactions in transgenic rats with ataxin-3-mediated ablation of hypothalamic orexin neurons.
abstract: Thermogenesis in brown adipose tissue (BAT) contributes to substantial increases in body temperature evoked by threatening or emotional stimuli. BAT thermogenesis also contributes to increases in body temperature that occur during active phases of the basic rest-activity cycle (BRAC), as part of normal daily life. Hypothalamic orexin-synthesizing neurons influence many physiological and behavioral variables, including BAT and body temperature. In conscious unrestrained animals maintained for 3 days in a quiet environment (24-26°C) with ad libitum food and water, we compared temperatures in transgenic rats with ablation of orexin neurons induced by expression of ataxin-3 (Orx_Ab) with wild-type (WT) rats. Both baseline BAT temperature and baseline body temperature, measured at the onset of BRAC episodes, were similar in Orx_Ab and WT rats. The time interval between BRAC episodes was also similar in the two groups. However, the initial slopes and amplitudes of BRAC-related increases in BAT and body temperature were reduced in Orx_Ab rats. Similarly, the initial slopes and amplitudes of the increases in BAT temperatures induced by sudden exposure to an intruder rat (freely moving or confined to a small cage) or by sudden exposure to live cockroaches were reduced in resident Orx_Ab rats. Constriction of the tail artery induced by salient alerting stimuli was also reduced in Orx_Ab rats. Our results suggest that orexin-synthesizing neurons contribute to the intensity with which rats interact with the external environment, both when the interaction is "spontaneous" and when the interaction is provoked by threatening or salient environmental events.
authors.affiliation: Centre for Neuroscience, Department of Human Physiology, Flinders University, Adelaide, South Australia, Australia; and mazher.mohammed@flinders.edu.au.
authors.forename: Mazher
authors.initials: M
authors.lastname: Mohammed
authors.affiliation: Centre for Neuroscience, Department of Human Physiology, Flinders University, Adelaide, South Australia, Australia; and.
authors.forename: Youichirou
authors.initials: Y
authors.lastname: Ootsuka
authors.affiliation: International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Japan; and Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Masashi
authors.initials: M
authors.lastname: Yanagisawa
authors.affiliation: Centre for Neuroscience, Department of Human Physiology, Flinders University, Adelaide, South Australia, Australia; and.
authors.forename: William
authors.initials: W
authors.lastname: Blessing
mesh_terms: D002001:Adipose Tissue, Brown / Q000502:physiology*; D000818:Animals; D000067699:Ataxin-3; D001522:Behavior, Animal / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D003058:Cockroaches; D004777:Environment; D007031:Hypothalamus / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009479:Neuropeptides / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000068797:Orexins; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D012039:Regional Blood Flow / Q000502:physiology; D012146:Rest / Q000502:physiology; D013623:Tail / Q000098:blood supply; D022722:Thermogenesis / Q000502:physiology*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D000068797:Orexins; D000067699:Ataxin-3; C511593:Atxn3 protein, rat
keywords: basic rest-activity cycle; body temperature; cutaneous blood flow; emotional hyperthermia; stress; thermoregulation; ultradian rhythm