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This Article Full Text Full Text (PDF) All Versions of this Article: 285/6/R1439    most recent 00198.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Furuyama, F. Articles by Nishino, H. Search for Related Content PubMed PubMed Citation Articles by Furuyama, F. Articles by Nishino, H.

INFLAMMATION, CYTOKINES, AND TEMPERATURE REGULATION

Regulation mode of evaporative cooling underlying a strategy of the heat-tolerant FOK rat for enduring ambient heat

¹Department of Neurophysiology and Brain Science, Nagoya City University Graduate School of Medical Sciences, Mizuho, Nagoya 467-8601; ²Department of Molecular Physiology, National Institute of Physiological Sciences, Okazaki 444-8585; ³Departments of Surgery, Physiology, and Cardiology and Center for Regenerative Medicine, Tokai University School of Medicine, Isehara 259-1193; and ⁴Department of Preventive Nutriceutical Sciences, Graduate School of Pharmaceutical Sciences, Nagoya City University, Tanabe Dori, Nagoya 467-8603, Japan

Submitted 14 April 2003 ; accepted in final form 15 August 2003

Compared with other rat strains, the inbred FOK rat is extremely heat tolerant. This increased heat tolerance is due largely to the animal's enhanced saliva spreading abilities. The aims of the present study were to 1) quantify the heat tolerance capacity of FOK rats and 2) determine the regulatory mode of the enhanced salivary cooling in these animals. Various strains of rats were acutely exposed to heat. In the heat-intolerant strains, saliva spreading was insufficient and the core temperature (T_c) rose rapidly. In contrast, FOK rats maintained an elevated T_c plateau (39.5 ± 0.7°C) for 5-6 h over a wide range of ambient temperatures (T_a) (37.5-42.5°C). In hot environments the FOK rats secreted copious amounts of saliva and spread it over more than the entire ventral body surface. FOK rats had a low T_c threshold for salivation, and the salivation rate increased linearly in proportion to the T_c deviation from the threshold. No strain difference or temperature effect was observed in the saliva secretion rate from in vitro submandibular glands perfused by sufficient doses of ACh. These results suggest that 1) the ability of FOK rats to maintain a moderate steady-state hyperthermia (39.5 ± 0.7°C) over a wide T_a range is enabled by a lowered threshold T_c for salivation and functional negative-feedback control of saliva secretion and 2) strain differences in ability to endure heat stress are mainly attributable to changes in the thermoregulatory control system rather than altered secretory abilities of the salivary glands.

body temperature regulation; salivation; heat stress; rat model; genotypic adaptation; biodefense