Orexin A (hypocretin 1) injected into hypothalamic paraventricular nucleus and spontaneous physical activity in rats
Open Access
- 1 April 2004
- journal article
- Published by American Physiological Society in American Journal of Physiology-Endocrinology and Metabolism
- Vol. 286 (4), E551-E559
- https://doi.org/10.1152/ajpendo.00126.2003
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 nonfeeding-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). O2 consumption and CO2 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 × 103 beam break count, n = 24; vehicle: 1.85 ± 1.13 × 103, n = 38). This increase in SPA was accompanied by compatible increase in O2 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.Keywords
This publication has 66 references indexed in Scilit:
- Fasting Activates the Nonhuman Primate Hypocretin (Orexin) System and Its Postsynaptic TargetsEndocrinology, 2003
- Hypothalamic gene expression in long-term fasted rats: relationship with body fatBiochemical and Biophysical Research Communications, 2003
- Decreased plasma orexin-A levels in obese individualsInternational Journal of Obesity, 2002
- Evidence that orexin-A-evoked grooming in the rat is mediated by orexin-1 (OX 1 ) receptors, with downstream 5-HT 2C receptor involvementPsychopharmacology, 2001
- Down-regulation of orexin gene expression by severe obesity in the rats: studies in Zucker fatty and Zucker diabetic fatty rats and effects of rosiglitazoneMolecular Brain Research, 2000
- Food intake elicited by central administration of orexins/hypocretins: identification of hypothalamic sites of actionBrain Research, 1999
- Narcolepsy in orexin Knockout MiceCell, 1999
- Orexins, orexigenic hypothalamic peptides, interact with autonomic, neuroendocrine and neuroregulatory systemsProceedings of the National Academy of Sciences, 1999
- Surgeon General's Report on Physical Activity and HealthJAMA, 1996
- The role of motor activity in diet-induced obesity in C57BL/6J micePhysiology & Behavior, 1996