Brown adipose tissue thermogenesis contributes to emotional hyperthermia in a resident rat suddenly confronted with an intruder rat

Abstract

There is controversy concerning the contribution of nonshivering thermogenesis in brown adipose tissue (BAT) to emotional hyperthermia. In the present study we compared BAT, core body, and brain temperature, and tail blood flow, simultaneously measured, to determine whether BAT thermogenesis contributes to emotional hyperthermia in a resident Sprague-Dawley rat when an intruder rat, either freely-moving or confined to a small cage, is suddenly introduced into the cage of the resident rat for 30 min. Introduction of the intruder rat promptly increased BAT, body, and brain temperatures in the resident rat. For the caged intruder these temperature increases were 1.4 Ϯ 0.2, 0.8 Ϯ 0.1, 1.0 Ϯ 0.1°C, respectively, with the increase in BAT temperature being significantly greater (P Ͻ 0.01) than the increases in body and brain. The initial 5-min slope of the BAT temperature record (0.18 Ϯ 0.02°C/min) was significantly greater (P Ͻ 0.01) than the corresponding value for body (0.10 Ϯ 0.01°C/min) and brain (0.09 Ϯ 0.02°C/min). Tail artery pulse amplitude fell acutely when the intruder rat was introduced, possibly contributing to the increases in body and brain temperature. Prior blockade of ␤3 adrenoceptors (SR59230A 10 mg/kg ip) significantly reduced the amplitude of each temperature increase. Intruder-evoked increases in BAT temperature were similar in resident rats maintained at 11°C for 3 days. In the caged intruder situation there is no bodily contact between the rats, so the stimulus is psychological rather than physical. Our study thus demonstrates that BAT thermogenesis contributes to increases in body and brain temperature occurring during emotional hyperthermia. body temperature; brain temperature; cutaneous blood flow; stressinduced hyperthermia; fever IN MAMMALS, BIRDS, AND REPTILES, body temperature may increase when individuals are placed in salient, emotionally significant situations, those relevant to the life and survival of the individual, a response sometimes referred to as "stressinduced hyperthermia" or "psychological fever" (5,8,18,31,32,35,40,44,60). The amplitude of the stress-related body temperature increase is similar in animals maintained at thermoneutrality or in a cold environment, so the response is not simply secondary to increased metabolism in skeletal and cardiac muscle. Rather, the temperature increases are initiated from the brain via active central command, supplementing homeostatic thermoregulatory processes. This is readily apparent when a lizard behaviorally increases its temperature by selecting a hotter environment after being released from manual restraint (10). In mammals, salient, emotionally arousing events also trigger vasoconstriction in the thermoregulatory cutaneous vascular beds, potentially contributing to emotional hyperthermia by reducing heat loss from the body (for references see Ref. 36).Most mammals have the capacity for facultative (nonshivering) thermogenesis such as that generated in brown adipose tissue (BAT), and heat produced by BAT is important for thermoregu...

Reduced brown adipose tissue thermogenesis during environmental interactions in transgenic rats with ataxin-3-mediated ablation of hypothalamic orexin neurons

“…In previous work for both BRAC and intruder models (35,45), we demonstrated that a ␤ 3 -adrenoceptor antagonist reduces the increases in both BAT and body temperatures. Similar findings have been reported in a social defeat model (29).…”

“…In one group of animals, the intruder rat was able to move freely inside the resident rat's cage. In another group, the intruder rat was confined to a smaller cage, preventing physical contact with the resident rat (35).…”

“…BAT thermogenesis also contributes to the rise in body temperature initiated by threatening environmental occurrences (emotional hyperthermia) (29,35). The occurrence of potentially threatening or salient environmental events also acutely decreases thermoregulatory cutaneous blood flow (34,35,63,64).…”

“…The occurrence of potentially threatening or salient environmental events also acutely decreases thermoregulatory cutaneous blood flow (34,35,63,64). We refer to these sudden changes in thermoregulatory cutaneous blood flow as sympathetic cutaneous vasomotor alerting responses (SCVARs) (15).…”

New insights on amygdala: Basomedial amygdala regulates the physiological response to social novelty

“…The animals remained in this condition for 15 min. This social novelty model has been adapted from two other models of social stress using intruder rats (Keeney et al, 2006;Mohammed et al, 2014).…”