Repeated Cold Stress Enhances the Acute Restraint Stress-Induced Hyperthermia in Mice.

The rodents exposed to repeated cold stress according to a specific schedule, known as specific alternation of rhythm in temperature (SART), exhibit autonomic imbalance, and is now used as an experimental model of fibromyalgia. To explore the susceptibility of SART-stressed animals to novel acute stress, we tested whether exposure of mice to SART stress for 1 week alters the extent of acute restraint stress-induced hyperthermia. Mice were subjected to 7-d SART stress sessions; i.e., the mice were alternately exposed to 24 and 4°C at 1-h intervals during the daytime (09:00-16:00) and kept at 4°C overnight (16:00-09:00). SART-stressed and unstressed mice were exposed to acute restraint stress for 20-60 min, during which rectal temperature was monitored. Serum corticosterone levels were measured before and after 60-min exposure to restraint stress. SART stress itself did not alter the body temperature or serum corticosterone levels in mice. Acute restraint stress increased the body temperature and serum corticosterone levels, both responses being greater in SART-stressed mice than unstressed mice. The enhanced hyperthermic responses to acute restraint stress in SART-stressed mice were significantly attenuated by SR59230A, a ß3 adrenoceptor antagonist, but unaffected by diazepam, an anxiolytic, mifepristone, a glucocorticoid receptor antagonist, or indomethacin, a cyclooxygenase inhibitor. These results suggest that SART stress enhances the susceptibility of mice to acute restraint stress, characterized by increased hyperthermia and corticosterone secretion, and that the increased hyperthermic responses to acute stress might involve accelerated activation of sympathetic ß3 adrenoceptors, known to regulate non-shivering thermogenesis in the brown adipose tissue.

Enhanced Hyperthermic Responses to Lipopolysaccharide in Mice Exposed to Repeated Cold Stress.

Lipopolysaccharide (LPS) induces hyperthermia accompanied by various other systemic inflammatory symptoms. The rodents exposed to repeated cold (RC) stress according to a specific schedule are useful as experimental models for autonomic imbalance or fibromyalgia. It is now proven that RC-stressed mice exhibit tolerance to LPS, we examined thermal responses to LPS challenge in RC-stressed mice by monitoring core temperature using the telemetry system. Systemic administration of LPS caused bimodal hyperthermic responses in RC-stressed and unstressed mice. The magnitude of the LPS-induced hyperthermia was greater in RC-stressed mice than in unstressed mice. The RC stress-induced enhancement of hyperthermic responses to LPS was abolished by pretreatment with diclofenac, which is a cyclooxygenase (COX) inhibitor. LPS did not significantly increase COX-2 protein levels in the lung or hypothalamus of RC-stressed or unstressed mice. RC stress did not alter baseline serum corticosterone levels or their increases in response to LPS challenge. These results suggest that RC stress enhances the susceptibility of mice to LPS challenge, leading to greater prostanoid-dependent hyperthermia, which might contribute to tolerance to LPS in RC-stressed mice.

[Comparison of lifestyle, mental stress, and medical check-up results between Tanshin-funin workers and workers living with their families].

OBJECTIVES: We conducted a comparative analysis of lifestyle, mental stress, and medical check-up results between tanshin-funin workers and workers living with their families. METHODS: Study participants were 3,026 married men, aged 40-59 yr, who worked at a large financial firm in Japan. Tanshin-funin was defined as married men separated from their families due to workplace assignments, as determined by a self-administered questionnaire in 2004. Participants' lifestyle factors, including exercise, alcohol and smoking consumption, and dietary habits, and mental stress, including lack of vigor, irritability, fatigue, anxiety, depressed mood, and physical complaints, were examined using a self-administered questionnaire. Medical check-ups conducted in 2004 included measurements of BMI, SBP, DBP, FBS, GOT, GPT, γ-GTP, TC, TG, HDL, RBC, and WBC. RESULTS: An analysis of lifestyle factors, using the χ(2) test, indicated that fewer tanshin-funin workers exercise, and that they had fewer regularly-scheduled meals. Tanshin-funin workers smoked more and consumed more alcohol, but ate fewer green and yellow vegetables. Tanshin-funin workers had fewer commuting hours and took fewer days off. Tanshin-funin workers also suffered more frequently from irritability and anxiety. A regression analysis, adjusted for age and smoking status, indicated that levels of TC, TG, and WBC for tanshin-funin workers were higher than workers living with their families. CONCLUSIONS: The lifestyle habits of tanshin-funin workers, such as dietary habits, were worse than those of workers living with their families, and tanshin-funin workers suffered from more irritability and anxiety. Clinical markers, such as dyslipidemia, were worse among tanshin-funin workers than among workers living with their families.