Brown fat thermogenesis and cardiac rate regulation during cold challenge in infant rats

Blumberg, Mark S.; Sokoloff, Greta; Kirby, Robert F.

doi:10.1152/ajpregu.1997.272.4.r1308

Cited by 24 publications

(38 citation statements)

References 25 publications

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“…In the ®rst group (balanced saline), all 4 pups were treated with saline. In the second group (balanced chlorisondamine), all 4 pups were treated with chlorisondamine, a ganglionic blocker that inhibits BAT thermogenesis (Blumberg, Sokoloff, & Kirby, 1997). In the third group (unbalanced), 2 pups were treated with saline and 2 pups were treated with chlorisondamine.…”

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confidence: 99%

Competition and cooperation among huddling infant rats

Sokoloff

Blumberg

2001

Developmental Psychobiology

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Huddling is expressed by infant rats and continues to be an important behavior throughout adulthood. As a form of behavioral thermoregulation, huddling is thought to play an essential role in compensating for inadequate physiological thermoregulation early in development. Infant rats, however, are capable of heat production shortly after birth using brown adipose tissue (BAT) and exhibit thermogenesis in the huddle, suggesting that huddling does not obviate the need for endothermy during cold exposure. In the present experiment, 4-pup huddles of infant rats (2- or 8-day-olds) were exposed to two subthermoneutral temperatures, and BAT thermogenesis was inhibited in 0, 2, or 4 of the rats in each huddle. Inhibition of BAT thermogenesis compromised the pups' ability to maintain huddle temperature, but surprisingly did not result in enhanced huddling at either age. These results suggest that effective huddling during cold exposure requires the thermal resources provided by endothermy. Furthermore, the heat provided by BAT appears to shape behavioral interactions in the huddle during development.

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confidence: 99%

Competition and cooperation among huddling infant rats

Sokoloff

Blumberg

2001

Developmental Psychobiology

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“…Perhaps the most significant and unique feature of the present experiment was the provisioning of a thermoneutral test environment in which body temperatures of infants at the ages used here are maintained at ϳ37°C (Blumberg et al, 1997). This feature of the experiment may be important for two reasons: First, hippocampal electrophysiological activity is influenced by local brain temperature (Andersen and Moser, 1995) and hippocampal slices from adult rats can be induced to exhibit theta-like activity only within a narrow thermal window of 33-37°C (Kowalczyk et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

“…At the end of this period, pups were intubated with commercial half-and-half and then transferred to an electrically shielded, double-walled glass chamber (height, 17 cm; inner diameter, 12.5 cm) through which temperaturecontrolled water was circulated. The air temperature inside the chamber was 35°C, which is within the thermoneutral range for newborn pups (Blumberg et al, 1997). Air flow through the chamber was 300 ml/min.…”

Section: Methodsmentioning

confidence: 99%

Hippocampal Theta in the Newborn Rat Is Revealed under Conditions That Promote REM Sleep

Karlsson

Blumberg

2003

J. Neurosci.

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Hippocampal theta activity, a high-amplitude, slow (4 -12 Hz) oscillation that occurs in a variety of behavioral contexts, is thought to emerge in infant rats only after 1 week of age. However, we report here that unanesthetized 2-and 4-d-old rats with electrodes implanted in the CA1 field of the hippocampus and tested in thermoneutral conditions exhibit theta activity. Moreover, this infant theta is characterized by the same neuronal bursting pattern and power spectrum that characterize theta in adults. Simultaneous measures of behavior and neck muscle tone indicated that bouts of theta occurred predominantly during periods of muscle atonia (with or without concurrent myoclonic twitching), indicative of REM sleep. In contrast, sharp waves were accompanied by startles (i.e., simultaneous and vigorous movement of all four limbs). These findings underscore the need for comprehensive in vivo investigations of the pharmacology, neural substrates, and behavioral correlates of hippocampal field activity in neonates.

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“…The procedures used in the present study have been fully described elsewhere 7 and are only briefly presented here. For experiment 1, an individual pup was removed from a litter on the day of testing, weighed, and placed in an incubator maintained at 35°C to 36°C.…”

Section: Methodsmentioning

confidence: 99%

“…[7][8][9] Specifically, heat produced by brown adipose tissue (BAT) during moderate cold exposure helps to warm cardiac muscle and by doing so contributes to the maintenance of cardiac rate. In contrast, pronounced bradycardia is produced by either extreme air temperatures that overwhelm the ability of BAT to deliver warm blood to cardiac muscle or ganglionic blockade that prevents the activation of BAT thermogenesis in response to the cold.…”

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Thermoregulatory and Cardiac Responses of Infant Spontaneously Hypertensive and Wistar-Kyoto Rats to Cold Exposure

et al. 1999

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Abstract-Cardiovascular function during cold exposure is dependent on effective thermoregulation. This dependence is particularly apparent in infants. For example, we have previously demonstrated that in infant rats during cold exposure, cardiac rate is directly related to their ability to produce heat endogenously. The primary source of endogenous heat production for infant rats is brown adipose tissue (BAT). Because of the dependence of cardiac rate on effective thermoregulation in the cold and because hypertension in spontaneously hypertensive rats (SHR) is influenced by the preweanling environment, in this study we examined the thermoregulatory and cardiac rate responses of infant SHR and Wistar-Kyoto rats (WKY) to varying levels of cold exposure. In experiment 1, 7-to 8-day-old SHR and WKY were acclimated at a thermoneutral air temperature (35°C) and then exposed to successive decreases in ambient temperature (30.5°C, 26.5°C, 23°C, and 17°C) while thermal and metabolic measures were recorded. Although both strains increased BAT thermogenesis and oxygen consumption in response to cold exposure, SHR cooled more than WKY and exhibited lower levels of oxygen consumption at the lowest air temperatures. Experiment 2 was identical to experiment 1 except that cardiac rate was also measured. Again, SHR exhibited substantial thermoregulatory deficits compared with WKY; in addition, they were less able than WKY to maintain cardiac rate at the 2 lowest air temperatures tested. Finally, in experiment 3, infant SHR exhibited diminished BAT thermogenesis in response to a range of doses of a selective ␤ 3 -adrenoceptor agonist. We hypothesize that long-term thermoregulatory deficits during the early postnatal period influence cardiovascular function and contribute to the development of hypertension in SHR. (Hypertension. 1999;33:1465-1469.)Key Words: body temperature regulation Ⅲ brown fat Ⅲ nonshivering thermogenesis Ⅲ heart rate Ⅲ rats, inbred strains Ⅲ hypertension, experimental T he degree of high blood pressure expressed in adult spontaneously hypertensive rats (SHR) is influenced by the neonatal environment. 1-3 Thus, manipulations limited to the preweanling period, such as cross-fostering, 2 pharmacological interventions, 1,4 and handling, 5,6 result in the lowering of blood pressure in adult SHR. Such findings highlight the importance of epigenetic processes in the development of established hypertension in SHR.We have recently demonstrated that thermoregulatory mechanisms play an important role in the protection of cardiovascular function during cold exposure in infant rats. [7][8][9] Specifically, heat produced by brown adipose tissue (BAT) during moderate cold exposure helps to warm cardiac muscle and by doing so contributes to the maintenance of cardiac rate. In contrast, pronounced bradycardia is produced by either extreme air temperatures that overwhelm the ability of BAT to deliver warm blood to cardiac muscle or ganglionic blockade that prevents the activation of BAT thermogenesis in response to the cold.T...

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Brown fat thermogenesis and cardiac rate regulation during cold challenge in infant rats

Cited by 24 publications

References 25 publications

Competition and cooperation among huddling infant rats

Competition and cooperation among huddling infant rats

Hippocampal Theta in the Newborn Rat Is Revealed under Conditions That Promote REM Sleep

Thermoregulatory and Cardiac Responses of Infant Spontaneously Hypertensive and Wistar-Kyoto Rats to Cold Exposure

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