Thermal homeostasis in pregnant rats during heat stress

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Abstract

Sprague-Dawley rats exposed to inescapable heat stress maintained a controlled hyperthermia while increasing heat loss by cutaneous vasodilatation and by grooming behavior. In nonpregnant Ss, the evaporation of saliva groomed onto the body surfaces increased exponentially as a function of ambient temperature above 36|C. In contrast, Ss in an advanced stage of pregnancy became dependent on grooming behavior for thermoregulation of ambient temperatures of 30-36|C. This was associated with a decrease in the body temperature threshold for salivary secretion from the submaxillary gland, which then began at approximately the same body temperature as cutaneous vasodilatation. The pregnant Ss maintained a lower level of controlled hyperthermia during heat stress than did nonpregnant Ss. This appeared to result from a decreased production of metabolic heat, reduced insulation on the ventral surface, and an increased motivation to keep cool during heat stress. These changes met the increased need for thermolysis during pregnancy and provided for thermal homeostasis both in the pregnant rat and in the unborn fetuses. (35 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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