title: Histaminergic regulation of seasonal metabolic rhythms in Siberian hamsters.
abstract: We investigated whether histaminergic tone contributes to the seasonal catabolic state in Siberian hamsters by determining the effect of ablation of histaminergic neurons on food intake, metabolic rate and body weight. A ribosomal toxin (saporin) conjugated to orexin-B was infused into the ventral tuberomammillary region of the hypothalamus, since most histaminergic neurons express orexin receptors. This caused not only 75-80% loss of histaminergic neurons in the posterior hypothalamus, but also some loss of other orexin-receptor expressing cells e.g. MCH neurons. In the long-day anabolic state, lesions produced a transient post-surgical decrease in body weight, but the hamsters recovered and maintained constant body weight, whereas weight gradually increased in sham-lesioned hamsters. VO(2) in the dark phase was significantly higher in the lesioned hamsters compared to shams, and locomotor activity also tended to be higher. In a second study in short days, sham-treated hamsters showed the expected seasonal decrease in body weight, but weight remained constant in the lesioned hamsters, as in the long-day study. Lesioned hamsters consumed more during the early dark phase and less during the light phase due to an increase in the frequency of meals during the dark and decreased meal size during the light, and their cumulative food intake in their home cages was greater than in the control hamsters. In summary, ablation of orexin-responsive cells in the posterior hypothalamus blocks the short-day induced decline in body weight by preventing seasonal hypophagia, evidence consistent with the hypothesis that central histaminergic mechanisms contribute to long-term regulation of body weight.
authors.affiliation: Biology Department, Washington and Lee University, Lexington, VA, USA.
authors.forename: Helen
authors.initials: H
authors.lastname: I'anson
authors.forename: Preeti H
authors.initials: PH
authors.lastname: Jethwa
authors.forename: Amy
authors.initials: A
authors.lastname: Warner
authors.forename: Francis J P
authors.initials: FJ
authors.lastname: Ebling
mesh_terms: D002001:Adipose Tissue, Brown / Q000187:drug effects; D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D006224:Cricetinae; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D006632:Histamine / Q000378:metabolism*; D006640:Histidine Decarboxylase / Q000378:metabolism; D007028:Hypothalamic Hormones / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D000922:Immunotoxins / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D008543:Melanins / Q000378:metabolism; D009479:Neuropeptides / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology; D000068797:Orexins; D010101:Oxygen Consumption / Q000187:drug effects; D017111:Phodopus; D010907:Pituitary Hormones / Q000378:metabolism; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology; D054789:Ribosome Inactivating Proteins, Type 1 / Q000494:pharmacology; D000076985:Saporins; D012621:Seasons; D013997:Time Factors
chemical_list: D007028:Hypothalamic Hormones; D000922:Immunotoxins; D047908:Intracellular Signaling Peptides and Proteins; D008543:Melanins; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D000068797:Orexins; D010907:Pituitary Hormones; D054789:Ribosome Inactivating Proteins, Type 1; C019463:melanin-concentrating hormone; D006632:Histamine; D000076985:Saporins; D006640:Histidine Decarboxylase