Selected Contribution: Ambient temperature for experiments  in rats: a new method for determining the zone  of thermal neutrality

Romanovsky, Andrej A.; Ivanov, Andrei I.; Shimansky, Yury P.

doi:10.1152/japplphysiol.01173.2001

Cited by 316 publications

(307 citation statements)

References 44 publications

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“…spreading, postural changes, and heat escape behavior (26,51). T CORE is also influenced by numerous other factors, such as respiratory rate, the surface to mass ratio, insulation, and integration with homeostatic systems controlling water balance and food intake (51).…”

Section: Discussionmentioning

confidence: 99%

“…3B). The heat loss index (HLI), an index of tail skin vasomotion that controls for ambient and core temperatures (26), was also consistently lower in NK 3 -SAP rats than Blank-SAP controls (Table 1). These results indicate that KNDy-ablated rats have lower levels of tail skin vasodilatation than Blank-SAP controls.…”

mentioning

confidence: 95%

“…Cutaneous vasodilatation of the rat's tail is a major heat-defense effector that can be evaluated indirectly by measuring changes in tail skin temperature (T SKIN ) (26,27). The vasomotor state of the tail varies across the estrous cycle, with the lowest levels of vasodilatation on proestrous night, when estrogen levels are high (28).…”

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confidence: 99%

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Role for kisspeptin/neurokinin B/dynorphin (KNDy) neurons in cutaneous vasodilatation and the estrogen modulation of body temperature

Mittelman-Smith

Williams

Krajewski-Hall

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

156

103

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Estrogen withdrawal in menopausal women leads to hot flushes, a syndrome characterized by the episodic activation of heat dissipation effectors. Despite the extraordinary number of individuals affected, the etiology of flushes remains an enigma. Because menopause is accompanied by marked alterations in hypothalamic kisspeptin/neurokinin B/dynorphin (KNDy) neurons, we hypothesized that these neurons could contribute to the generation of flushes. To determine if KNDy neurons participate in the regulation of body temperature, we evaluated the thermoregulatory effects of ablating KNDy neurons by injecting a selective toxin for neurokinin-3 expressing neurons [NK 3 -saporin (SAP)] into the rat arcuate nucleus. Remarkably, KNDy neuron ablation consistently reduced tail-skin temperature (T SKIN ), indicating that KNDy neurons facilitate cutaneous vasodilatation, an important heat dissipation effector. Moreover, KNDy ablation blocked the reduction of T SKIN by 17β-estradiol (E 2 ), which occurred in the environmental chamber during the light phase, but did not affect the E 2 suppression of T SKIN during the dark phase. At the high ambient temperature of 33°C, the average core temperature (T CORE ) of ovariectomized (OVX) control rats was significantly elevated, and this value was reduced by E 2 replacement. In contrast, the average T CORE of OVX, KNDy-ablated rats was lower than OVX control rats at 33°C, and not altered by E 2 replacement. These data provide unique evidence that KNDy neurons promote cutaneous vasodilatation and participate in the E 2 modulation of body temperature. Because cutaneous vasodilatation is a cardinal sign of a hot flush, these results support the hypothesis that KNDy neurons could play a role in the generation of flushes.reproduction | gonadotropin-releasing hormone | thermoregulation E strogen withdrawal leads to hot flushes in the majority of menopausal women (1). Hot flushes are also experienced by men and women treated with tamoxifen for breast cancer, men undergoing androgen-ablation therapy for prostate cancer, young oophorectomized women, and hypogonadal men (2, 3). A hot flush is characterized by episodic activation of heat dissipation effectors, including cutaneous vasodilatation, sweating, and behavioral thermoregulation. After a flush is initiated, the activation of heat dissipation mechanisms is so effective that core temperature frequently drops (4). Despite the vast numbers of individuals affected, the etiology of flushes remains an enigma.Hot flushes are closely timed with luteinizing hormone (LH) pulses, providing a clue that the generation of flushes is linked to the hypothalamic neural circuitry controlling pulsatile gonadotropin-releasing hormone (GnRH) secretion (5, 6). Current evidence suggests that pulsatile GnRH secretion is modulated by a subpopulation of neurons in the arcuate (infundibular) nucleus that express estrogen receptor α (ERα), neurokinin 3 receptor (NK 3 R), kisspeptin, neurokinin B (NKB), and dynorphin (7-11). In the hypothalamus of postmenopausal women, ...

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Section: Discussionmentioning

confidence: 99%

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confidence: 95%

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Role for kisspeptin/neurokinin B/dynorphin (KNDy) neurons in cutaneous vasodilatation and the estrogen modulation of body temperature

Mittelman-Smith

Williams

Krajewski-Hall

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

156

103

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“…During the next two sessions, we examined the effects of saline and methylone or MDPV (9 or 1 mg/kg, respectively) at 29 1C ambient temperatures. Although this temperature is 6-7 1C higher than standard housing conditions (22-23 1C), it corresponds to the thermoneutral zone in rats, where endogenous heat production is minimal and balanced with heat loss (Romanovsky et al, 2002). In all experiments, we recorded temperature and locomotion for at least 5 h after drug or saline injections.…”

Section: Methodsmentioning

confidence: 99%

Effects of Social Interaction and Warm Ambient Temperature on Brain Hyperthermia Induced by the Designer Drugs Methylone and MDPV

Kiyatkin

Kim

Wakabayashi

et al. 2014

Neuropsychopharmacol

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3,4-Methylenedioxymethcathinone (methylone) and 3,4-methylenedioxypyrovalerone (MDPV) are new drugs of abuse that have gained worldwide popularity. These drugs are structurally similar to 3,4-methylenedioxymethamphetamine (MDMA) and share many of its physiological and behavioral effects in humans, including the development of hyperthermia during acute intoxication. Here, we examined the effects of methylone (1-9 mg/kg, s.c.) or MDPV (0.1-1.0 mg/kg, s.c.) on brain temperature homeostasis in rats maintained in a standard laboratory environment (single-housed in a quiet rest at 22 1C) and under conditions that model human drug use (social interaction and 29 1C ambient temperature). By simultaneously monitoring temperatures in the nucleus accumbens, temporal muscle, and facial skin, we assessed the effects of methylone and MDPV on intra-brain heat production and cutaneous vascular tone, two critical factors that control brain temperature responses. Both methylone and MDPV dose-dependently increased brain temperature, but even at high doses that induced robust locomotor activation, hyperthermia was modest in magnitude (up to B2 1C). Both drugs also induced dose-dependent peripheral vasoconstriction, which appears to be a primary mechanism determining the brain hyperthermic responses. In contrast to the powerful potentiation of MDMA-induced hyperthermia by social interaction and warm ambient temperature, such potentiation was absent for methylone and minimal for MDPV. Taken together, despite structural similarities to MDMA, exposure to methylone or MDPV under conditions commonly associated with human drug use does not lead to profound elevations in brain temperature and sustained vasoconstriction, two critical factors associated with MDMA toxicity.

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“…Empirical studies of the TNZ are local descriptions contingent on the particular combinations of air temperature, wind speed, radiation, and humidity used in the experiment, fur properties, size, and shape. Statistical descriptions derived from them cannot be used to generalize TNZs in other environments (11,12). Instead, we need a mechanistic approach to understand how evolutionary changes in key traits such as size and shape relate to energy and water costs across natural environmental gradients.…”

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confidence: 99%

Size, shape, and the thermal niche of endotherms

Porter

Kearney

2009

Proc. Natl. Acad. Sci. U.S.A.

220

236

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A key challenge in ecology is to define species' niches on the basis of functional traits. Size and shape are important determinants of a species' niche but their causal role is often difficult to interpret. For endotherms, size and shape define the thermal niche through their interaction with core temperature, insulation, and environmental conditions, determining the thermoneutral zone (TNZ) where energy and water costs are minimized. Laboratory measures of metabolic rate used to describe TNZs cannot be generalized to infer the capacity for terrestrial animals to find their TNZ in complex natural environments. Here, we derive an analytical model of the thermal niche of an ellipsoid furred endotherm that accurately predicts field and laboratory data. We use the model to illustrate the relative importance of size and shape on the location of the TNZ under different environmental conditions. The interaction between body shape and posture strongly influences the location of the TNZ and the expected scaling of metabolic rate with size at constant temperature. We demonstrate that the latter relationship has a slope of approximately 1 ⁄2 rather than the commonly expected surface area/volume scaling of 2 ⁄3. We show how such functional traits models can be integrated with spatial environmental datasets to calculate null expectations for body size clines from a thermal perspective, aiding mechanistic interpretation of empirical clines such as Bergmann's Rule. The combination of spatially explicit data with biophysical models of heat exchange provides a powerful means for studying the thermal niches of endotherms across climatic gradients.biophysical ecology ͉ functional traits ͉ lower critical temperature ͉ metabolic scaling ͉ thermoneutral zone T he ecological niche reflects the interaction between an organism and its environment and how that interaction affects its fitness (1, 2). An understanding of a species' niche requires knowledge of its traits (morphology, physiology, and behavior) and how that species interacts with its habitat to construct environments (2). This two-way interaction between organism and environment is also key to understanding how a species' traits, and hence its niche, evolves (3, 4). A species' energy and water balance are key determinants of its niche, reflecting both its requirements for life (Grinnellian niche) and its impact on the other species with which it interacts (Eltonian niche). Here, we illustrate how biophysical principles can be used to link variation in the size, shape, and other functional traits of organisms with environmental data to predict the thermal niches of endotherms. Such a model can be conceived as a mechanistic depiction of the Hutchinsonian niche, a hypervolume describing conditions suitable for survival, growth, and reproduction along trait and environmental axes. Biophysical models provide a way to calculate spatially explicit null models of selective pressures on functional traits from the perspectives of energy and water conservation (5).Basal metabolic rate ...

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Selected Contribution: Ambient temperature for experiments in rats: a new method for determining the zone of thermal neutrality

Cited by 316 publications

References 44 publications

Role for kisspeptin/neurokinin B/dynorphin (KNDy) neurons in cutaneous vasodilatation and the estrogen modulation of body temperature

Role for kisspeptin/neurokinin B/dynorphin (KNDy) neurons in cutaneous vasodilatation and the estrogen modulation of body temperature

Effects of Social Interaction and Warm Ambient Temperature on Brain Hyperthermia Induced by the Designer Drugs Methylone and MDPV

Size, shape, and the thermal niche of endotherms

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