Stress increases cardiac function, ventilation, and body temperature. These changes will prepare to and support for fight-or-flight behavior by increasing supply of fuel and oxygen and by increasing conduction velocity of nerve impulses. We previously demonstrated that cardiorespiratory excitation during stress depends on hypothalamic neuropeptide, orexin (review: Resp Physiol Neurobiol 174: 43-54, 2010). We examined whether the same is true for stress-induced hyperthermia. Orexin neuron-ablated mice (ORX-AB) showed an attenuated stress-induced hyperthermia while their basal body temperature is normal. The brown adipose tissue, which is a major thermogenic organ in rodents, did not respond to handling stress although it did respond to a direct pharmacologic stimulation. These abnormalities in ORX-AB were not observed in orexin knockout mice in which orexin peptide is deficient but neurons are preserved. Therefore, integrity (orexin and co-existing other neurotransmitter/modulators) of the orexin neurons is indispensable for full expression of multiple facets of the fight-or-flight response.
J Physiol 588 (21): 4117-4129, 2010. (see also perspectives p. 4067)
*Department of Molecular & Integrative Physiology, Chiba University Graduate School of Medicine