Proceedings of The Physiological Society

University College Dublin (2009) Proc Physiol Soc 15, C117

Oral Communications

Effects of exogenously induced fever and hyperthermia on endocrine functions and behavior in the pre-pubertal rat

F. Mete1, E. Kilic2, A. Somay3, B. Yilmaz2

1. Pediatrics, Vakif Gureba Education and Research Hospital, Istanbul, Turkey. 2. Physiology, Yeditepe University, Faculty of Medicine, Istanbul, Turkey. 3. Pathology, Vakif Gureba Education and Research Hospital, Istanbul, Turkey.

Hyperthermia may cause pathological changes in various organs including the endocrine system and brain. In this study, we examined effects of exogenously induced fever and hyperthermia on adrenal and thyroid functions and behaviors in pre-pubertal male Sprague-Dawley rats. Three groups of 30-day old rats were used. Body temperature was increased to 39°C (fever; Group I) and 41°C (hyperthermia; Group II) in a hyperthermia induction chamber for 30 min. The rats in the Group III served as control (36 °C). Temperature of the laboratory was 21°C. Core temperature of the animals was monitored by using a rectal probe throughout the experiments. All animals received saline (0.2 ml x 4 times, ip) and were decapitated 48 h after the experiments (day 32). Blood samples were collected. Serum cortisol, fT3, fT4 and dehydroepiandrosterone (DHEA) levels were determined by chemiluminescence assay. Pituitary and adrenal glands were dissected out and processed for histopathological examination. To assess the activity and anxiety of the animals, the open field test and elevated-0-maze test, respectively, were used in all groups 24h before (day 29) and after (day 31) hyperthermia induction. Experiments were approved by the local ethics committee. Results were statistically analyzed by using One-Way Analysis of Variance followed by LSD test. Serum cortisol levels (3.22±1.3) were significantly reduced in the fever (1.3±0.9) and hyperthermia (1.09±0.7) induced groups (p<0.01). Serum levels of thyroid hormones did not significantly differ among the groups. DHEA values were below the limit of detection in all groups. Histopathological examination revealed that fever caused hyperemia in the pituitary and adrenal glands. However, mild degeneration was observed in both glands in the hyperthermia group. Progression time in the open field test was significantly decreased and anxiety test scores increased in animals exposed to 39°C compared to the control values (p<0.01). These parameters were more pronounced in the hyperthermia group (p<0.01). In conclusion, hyperthermia induced stress may cause delayed reduction in serum cortisol levels which may be associated with behavioral abnormalities in pre-pubertal male rats.

Where applicable, experiments conform with Society ethical requirements