Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N6‐cyclohexyladenosine‐induced hibernation in the Arctic ground squirrel (Urocitellus parryii). Issue 3 (29th August 2019)

• Record Type: Journal Article
• Authors: Frare, Carla; Jenkins, Mackenzie E.; McClure, Kelsey M.; Drew, Kelly L.
• Is Part Of: Journal of neurochemistry. Volume 151:Issue 3(2019)
• Page Start: 316
• Page End: 335
• Publication Date: 2019-08-29
• Subjects: cFos -- MnPO -- NTS -- raphe -- thermoregulation -- TMN; Neurochemistry -- Periodicals; 616.8042
• DOI: 10.1111/jnc.14814
• Languages: English
• ISSNs: 0022-3042

Abstract

Abstract: Hibernation is a seasonal phenomenon characterized by a drop in metabolic rate and body temperature. Adenosine A1 receptor agonists promote hibernation in different mammalian species, and the understanding of the mechanism inducing hibernation will inform clinical strategies to manipulate metabolic demand that are fundamental to conditions such as obesity, metabolic syndrome, and therapeutic hypothermia. Adenosine A1 receptor agonist‐induced hibernation in Arctic ground squirrels is regulated by an endogenous circannual (seasonal) rhythm. This study aims to identify the neuronal mechanism underlying the seasonal difference in response to the adenosine A1 receptor agonist. Arctic ground squirrels were implanted with body temperature transmitters and housed at constant ambient temperature (2°C) and light cycle (4L:20D). We administered CHA (N 6 ‐cyclohexyladenosine), an adenosine A1 receptor agonist in euthermic‐summer phenotype and euthermic‐winter phenotype and used cFos and phenotypic immunoreactivity to identify cell groups affected by season and treatment. We observed lower core and subcutaneous temperature in winter animals and CHA produced a hibernation‐like response in winter, but not in summer. cFos‐ir was greater in the median preoptic nucleus and the raphe pallidus in summer after CHA. CHA administration also resulted in enhanced cFos‐ir in the nucleus tractus solitarius and decreased cFos‐ir in the tuberomammillary nucleus in both seasons. In winter, cFos‐ir was greater in the supraoptic nucleus and lower in the raphe pallidus than in summer. The seasonal decrease in the thermogenic response to CHA and the seasonal increase in vasoconstriction, assessed by subcutaneous temperature, reflect the endogenous seasonal modulation of the thermoregulatory systems necessary for CHA‐induced hibernation. Cover Image for this issue: doi: 10.1111/jnc.14528 . Abstract : Adenosine promotes hibernation and torpor through the A1 receptor. However, an endogenous seasonal rhythm regulates the response to adenosine A1 receptor agonist‐induced hibernation in Arctic ground squirrels. We hypothesized that thermoregulation is seasonally modulated. Using immunohistochemical analyses in brain tissue of Arctic ground squirrels, we identify the median preoptic area (MnPO) and raphe pallidus (rPA) as the main brain nuclei regulating the seasonal difference in response to CHA, an adenosine A1 receptor agonist. The seasonal increase in vasoconstriction, measured by subcutaneous body temperature and associated with higher cFos expression in the supraoptic nucleus (SON), explains the delayed fall in Tb observed in winter ground squirrels after CHA. Cover Image for this issue: doi: 10.1111/jnc.14528 . Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/