Orexin A (hypocretin 1) injected into hypothalamic paraventricular nucleus and spontaneous physical activity in rats

Kohji Kiwaki, Catherine M. Kotz, Chuanfeng Wang, Lorraine Lanningham-Foster, James A. Levine

Research output: Contribution to journalArticle

107 Citations (Scopus)

Abstract

In humans, nonexercise activity thermogenesis (NEAT) increases with positive energy balance, The mediator of the interaction between positive energy balance and physical activity is unknown. In this study, we address the hypothesis that orexin A acts in the hypothalamic paraventricular nucleus (PVN) to increase non-feeding-associated physical activity. PVN-cannulated rats were injected with either orexin A or vehicle during the light and dark cycle. Spontaneous physical activity (SPA) was measured using arrays of infrared activity sensors and night vision videotaped recording (VTR). O 2 consumption and CO 2 production were measured by indirect calorimetry. Feeding behavior was assessed by VTR. Regardless of the time point of injection, orexin A (1 nmol) was associated with dramatic increases in SPA for 2 h after injection (orexin A: 6.27 ± 1.95 × 10 3 beam break count, n = 24; vehicle: 1.85 ± 1.13 × 10 3, n = 38). This increase in SPA was accompanied by compatible increase in O 2 consumption. Duration of feeding was increased only when orexin A was injected in the early light phase and accounted for only 3.5 ± 2.5% of the increased physical activity. In a dose-response experiment, increases in SPA were correlated with dose of orexin A linearly up to 2 nmol. PVN injections of orexin receptor antagonist SB-334867 were associated with decreases in SPA and attenuated the effects of PVN-injected orexin A. Thus orexin A can act in PVN to increase nonfeeding-associated physical activity, suggesting that this neuropeptide might be a mediator of NEAT.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume286
Issue number4 49-4
DOIs
StatePublished - Apr 2004
Externally publishedYes

Fingerprint

Paraventricular Hypothalamic Nucleus
Rats
Thermogenesis
Energy balance
Injections
Night Vision
Indirect Calorimetry
Orexins
Photoperiod
Feeding Behavior
Calorimetry
Carbon Monoxide
Neuropeptides
Human Activities
Infrared radiation
Light
Sensors

Keywords

  • Energy expenditure
  • Hypothalamus
  • Nonexercise activity thermogenesis
  • Obesity

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry

Cite this

Orexin A (hypocretin 1) injected into hypothalamic paraventricular nucleus and spontaneous physical activity in rats. / Kiwaki, Kohji; Kotz, Catherine M.; Wang, Chuanfeng; Lanningham-Foster, Lorraine; Levine, James A.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 286, No. 4 49-4, 04.2004.

Research output: Contribution to journalArticle

Kiwaki, Kohji ; Kotz, Catherine M. ; Wang, Chuanfeng ; Lanningham-Foster, Lorraine ; Levine, James A. / Orexin A (hypocretin 1) injected into hypothalamic paraventricular nucleus and spontaneous physical activity in rats. In: American Journal of Physiology - Endocrinology and Metabolism. 2004 ; Vol. 286, No. 4 49-4.
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AB - In humans, nonexercise activity thermogenesis (NEAT) increases with positive energy balance, The mediator of the interaction between positive energy balance and physical activity is unknown. In this study, we address the hypothesis that orexin A acts in the hypothalamic paraventricular nucleus (PVN) to increase non-feeding-associated physical activity. PVN-cannulated rats were injected with either orexin A or vehicle during the light and dark cycle. Spontaneous physical activity (SPA) was measured using arrays of infrared activity sensors and night vision videotaped recording (VTR). O 2 consumption and CO 2 production were measured by indirect calorimetry. Feeding behavior was assessed by VTR. Regardless of the time point of injection, orexin A (1 nmol) was associated with dramatic increases in SPA for 2 h after injection (orexin A: 6.27 ± 1.95 × 10 3 beam break count, n = 24; vehicle: 1.85 ± 1.13 × 10 3, n = 38). This increase in SPA was accompanied by compatible increase in O 2 consumption. Duration of feeding was increased only when orexin A was injected in the early light phase and accounted for only 3.5 ± 2.5% of the increased physical activity. In a dose-response experiment, increases in SPA were correlated with dose of orexin A linearly up to 2 nmol. PVN injections of orexin receptor antagonist SB-334867 were associated with decreases in SPA and attenuated the effects of PVN-injected orexin A. Thus orexin A can act in PVN to increase nonfeeding-associated physical activity, suggesting that this neuropeptide might be a mediator of NEAT.

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