On the role of anesthesia on the body/brain temperature differential in rats

Zhu, Min; Nehra, Deepika; Ackerman, Joseph J. H.; Yablonskiy, Dmitriy A.

doi:10.1016/j.jtherbio.2004.08.029

Cited by 38 publications

(23 citation statements)

References 30 publications

(29 reference statements)

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“…In cats, for example, during halothane and pentobarbital anesthesia with body warming cortical tissue was, respectively, 1.0 and 1.8°C colder than body core (Erikson and Lanier 2003). Similar negative brain-body temperature diVerentials were found during pentobarbital anesthesia in dogs (Wass et al 1998), urethane anesthesia in rats (Moser and Mathiesen 1996), and anesthesia induced by alpha-chloralose and chloral hydrate in rats (Zhu et al 2004). In the latter study, when alphachloralose was combined with body warming, the diVerence between cortex and core body reached 4.3°C.…”

Section: Brain Hypothermia During General Anesthesiasupporting

confidence: 62%

Brain temperature fluctuations during physiological and pathological conditions

Kiyatkin

2007

Eur J Appl Physiol

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This review discusses brain temperature as a physiological parameter, which is determined primarily by neural metabolism, regulated by cerebral blood flow, and affected by various environmental factors and drugs. First, we consider normal fluctuations in brain temperature that are induced by salient environmental stimuli and occur during motivated behavior at stable normothermic conditions. Second, we analyze changes in brain temperature induced by various drugs that affect brain and body metabolism and heat dissipation. Third, we consider how these physiological and drug-induced changes in brain temperature are modulated by environmental conditions that diminish heat dissipation. Our focus is psychomotor stimulant drugs and brain hyperthermia as a factor inducing or potentiating neurotoxicity. Finally, we discuss how brain temperature is regulated, what changes in brain temperature reflect, and how these changes may affect neural functions under normal and pathological conditions. Although most discussed data were obtained in animals and several important aspects of brain temperature regulation in humans remain unknown, our focus is on the relevance of these data for human physiology and pathology.

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Section: Brain Hypothermia During General Anesthesiasupporting

confidence: 62%

Brain temperature fluctuations during physiological and pathological conditions

Kiyatkin

2007

Eur J Appl Physiol

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“…On the basis of computer models of adult Wistar rats an approach to the permitted non-thermal SAR limit was numerically found around 8 W/kg (2.3 g brain-averaged) and the SAR of 8.2 W/kg was therefore used here as the maximum starting value. The curves show a rather long-lasting temperature increase in dead rats and a substantially reduced temperature effect in narcotized rats due to the blood flow and due to the active though still damped thermal regulation [20], [21], [22], [23]. Since only two parameters are important (1. the starting slope of the temperature curve being proportional to SAR, and 2. the temperature maximum), the measurements with narcotized animals were terminated when a stabilization of the curves became obvious.…”

Section: Resultsmentioning

confidence: 99%

Electromagnetic Field Effect or Simply Stress? Effects of UMTS Exposure on Hippocampal Longterm Plasticity in the Context of Procedure Related Hormone Release

et al. 2011

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Harmful effects of electromagnetic fields (EMF) on cognitive and behavioural features of humans and rodents have been controversially discussed and raised persistent concern about adverse effects of EMF on general brain functions. In the present study we applied radio-frequency (RF) signals of the Universal Mobile Telecommunications System (UMTS) to full brain exposed male Wistar rats in order to elaborate putative influences on stress hormone release (corticosteron; CORT and adrenocorticotropic hormone; ACTH) and on hippocampal derived synaptic long-term plasticity (LTP) and depression (LTD) as electrophysiological hallmarks for memory storage and memory consolidation. Exposure was computer controlled providing blind conditions. Nominal brain-averaged specific absorption rates (SAR) as a measure of applied mass-related dissipated RF power were 0, 2, and 10 W/kg over a period of 120 min. Comparison of cage exposed animals revealed, regardless of EMF exposure, significantly increased CORT and ACTH levels which corresponded with generally decreased field potential slopes and amplitudes in hippocampal LTP and LTD. Animals following SAR exposure of 2 W/kg (averaged over the whole brain of 2.3 g tissue mass) did not differ from the sham-exposed group in LTP and LTD experiments. In contrast, a significant reduction in LTP and LTD was observed at the high power rate of SAR (10 W/kg). The results demonstrate that a rate of 2 W/kg displays no adverse impact on LTP and LTD, while 10 W/kg leads to significant effects on the electrophysiological parameters, which can be clearly distinguished from the stress derived background. Our findings suggest that UMTS exposure with SAR in the range of 2 W/kg is not harmful to critical markers for memory storage and memory consolidation, however, an influence of UMTS at high energy absorption rates (10 W/kg) cannot be excluded.

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“…The situation can be dramatically different under anesthesia when the blood flow may be much lower than in the awaked state, and the characteristic length becomes bigger (3-4 mm). Because this characteristic length is comparable with the size of small animal brain, the baseline temperature distribution may become inhomogeneous across the whole brain and can lead to significant global baseline temperature decreases in the entire brain (25). This effect can be exaggerated if the brain is exposed to the environment.…”

Section: Discussionmentioning

confidence: 99%

“…Although brain insulation by cerebrospinal fluid, skull, scalp, and hair is also important (see detailed discussion in ref. 20), these effects are especially significant in small animals and͞or in case of exposed brain, where direct intraoperative temperature measurements (15,(22)(23)(24)(25) demonstrated that the superficial brain temperature is lower than the deep brain temperature by several degrees. A computer model of temperature changes in the human calcarine fissure during functional activation (26) predicted that the temperature changes in this structure could be both positive and negative, depending mostly on the distance from the brain surface.…”

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confidence: 99%

Theoretical model of temperature regulation in the brain during changes in functional activity

Sukstanskiı̆

Yablonskiy

2006

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

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The balance between metabolic heat production, heat removal by blood flow, and heat conductance defines local temperature distribution in a living tissue. Disproportional local increases in blood flow as compared with oxygen consumption during functional brain activity disturb this balance, leading to temperature changes. In this article we have developed a theoretical framework that allows analysis of temperature changes during arbitrary functional brain activity. We established theoretical boundaries on temperature changes and explained how these boundaries depend on physiology (blood flow and metabolism) and external (heat exchange with the environment) experimental conditions. We show that, in regions located deep in the brain, task performance should be accompanied by temperature decreases in regions where blood flow increases (activated regions) and by temperature increases in regions where blood flow decreases (deactivated regions). The sign of temperature effect may be reversed for superficial cortex regions, where the baseline brain temperature is lower than the temperature of incoming arterial blood due to the heat exchange with the environment. Importantly, due to heat conductance, the temperature effect is not localized to the activated region but extends to a surrounding tissue at rest over the distances regulated by the temperature-shielding effect of blood flow. This temperature-shielding effect quantifies the means by which cerebral blood flow prevents ''temperature perturbations'' from propagating away from the perturbed regions. For small activated regions, this effect also substantially suppresses the magnitude of the temperature response, making it especially important for small animal brains.brain temperature ͉ cerebral blood flow ͉ cerebral metabolism ͉ functional brain activity B asic mechanisms underlying global temperature regulation in humans and animals have attracted substantial attention from scientists, and considerable progress has been achieved in this area both in health and disease (see, e.g., refs. 1-4). However, information on brain temperature regulation, especially its relationship to function, is conflicting. Indeed, although, numerous experimental studies have demonstrated changes in the brain temperature of humans and animals upon functionally induced changes in brain activity, the magnitude and even sign of reported temperature changes vary substantially. For example, localized temperature variations from 0.01°C to 0.2°C were observed in animal brains (5-13) under different stimuli (visual, auditory, somatic). As reported in ref. 6, the sign of temperature response to visual stimulation in cats depends on the frequency of flashing light; for low frequencies (2-12 Hz), the temperature increases, whereas at high-frequencies (42-62 Hz) the temperature decreased. Negative temperature changes, on average Ϫ0.2°C, were observed in the deep regions of the visual cortex in conscious intact human subjects by a magnetic resonance method (14), whereas positive temperature changes up...

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On the role of anesthesia on the body/brain temperature differential in rats

Cited by 38 publications

References 30 publications

Brain temperature fluctuations during physiological and pathological conditions

Brain temperature fluctuations during physiological and pathological conditions

Electromagnetic Field Effect or Simply Stress? Effects of UMTS Exposure on Hippocampal Longterm Plasticity in the Context of Procedure Related Hormone Release

Theoretical model of temperature regulation in the brain during changes in functional activity

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