The overall goal is to characterize the role that body fat reserves and hypothalamic peptide mechanisms, especially neuropeptide Y (NPY), play in controlling daily torpor. Daily torpor is an extreme form of temperature regulation that evolved to help animals contend with limited food availability by uniquely reducing energy expenditure. The central and peripheral neural mechanisms integrating overall energy balance and torpor will be explored. Annual rhythms of food intake and body mass, reproduction, and daily torpor are well documented in the Siberian hamster (Phodopus sungorus), the model species in all experiments.
Specific aims i nclude: 1) contrasting the effects of direct intra-medial preoptic area (MPOA) injections of NPY on body temperature, specifically its ability to induce torpor and affect the timing of changes in brown adipose tissue temperature vs. body temperature;2) developing an anatomical understanding of the distribution of NPY receptor subtypes in the Siberian hamster hypothalamus;3) comparing and contrasting NPY receptor agonist activation and antagonist inhibition of NPY receptor sites in the MPOA on torpor induction;4) evaluating the necessity of the MPOA for both induced (NPY &2DG) and natural torpor using neuron-specific neurotoxic lesions;5) comparing and contrasting effects of direct injections of NPY and NPY receptor agonists into the paraventricular nucleus of the hypothalamus on interscapular brown adipose tissue temperature (and body temperature).
|Dark, John; Pelz, Kimberly M (2008) NPY Y1 receptor antagonist prevents NPY-induced torpor-like hypothermia in cold-acclimated Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 294:R236-45|
|Pelz, Kimberly M; Routman, David; Driscoll, Joseph R et al. (2008) Monosodium glutamate-induced arcuate nucleus damage affects both natural torpor and 2DG-induced torpor-like hypothermia in Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 294:R255-65|
|Pelz, Kimberly M; Dark, John (2007) ICV NPY Y1 receptor agonist but not Y5 agonist induces torpor-like hypothermia in cold-acclimated Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 292:R2299-311|
|Park, Jin Ho; Dark, John (2007) Fos-like immunoreactivity in Siberian hamster brain during initiation of torpor-like hypothermia induced by 2DG. Brain Res 1161:38-45|
|Dark, John (2005) Annual lipid cycles in hibernators: integration of physiology and behavior. Annu Rev Nutr 25:469-97|
|Paul, Matthew J; Freeman, David A; Park, Jin Ho et al. (2005) Neuropeptide Y induces torpor-like hypothermia in Siberian hamsters. Brain Res 1055:83-92|
|Freeman, David A; Lewis, Daniel A; Kauffman, Alexander S et al. (2004) Reduced leptin concentrations are permissive for display of torpor in Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 287:R97-R103|
|Dark, J; Miller, D R; Lewis, D A et al. (2003) Noradrenaline-induced lipolysis in adipose tissue is suppressed at hibernation temperatures in ground squirrels. J Neuroendocrinol 15:451-8|
|Lewis, D; Freeman, D A; Dark, J et al. (2002) Photoperiodic control of oestrous cycles in Syrian hamsters: mediation by the mediobasal hypothalamus. J Neuroendocrinol 14:294-9|
|Bae, H H; Stamper, J L; Heydorn, E C et al. (2000) Role of area postrema in control of torpor in Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 279:R591-8|
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