Active coping with stress suppresses glucose metabolism in the rat hypothalamus

Abstract

We used ¹⁸F-fluorodeoxyglucose small-animal positron-emission tomography to determine whether different styles of coping with stress are associated with different patterns of neuronal activity in the hypothalamus. Adult rats were subjected to immobilization (IMO)-stress or to a non-immobilized condition for 30 min, in random order on separate days, each of which was followed by brain-scanning. Some rats in the immobilized condition were allowed to actively cope with the stress by chewing a wooden stick during IMO, while the other immobilized rats were given nothing to chew on. Voxel-based statistical analysis of the brain imaging data shows that chewing counteracted the stress-induced increased glucose uptake in the hypothalamus to the level of the non-immobilized condition. Region-of-interest analysis of the glucose uptake values further showed that chewing significantly suppressed stress-induced increased glucose uptake in the paraventricular hypothalamic nucleus and the anterior hypothalamic area but not in the lateral hypothalamus. Together with the finding that the mean plasma corticosterone concentration at the termination of the IMO was also significantly suppressed when rats had an opportunity to chew a wooden stick, our results showed that active coping by chewing inhibited the activation of the hypothalamic–pituitary–adrenal axis to reduce the endocrine stress response.

Keywords::

• Chewing
• corticosterone
• ¹⁸F-fluorodeoxyglucose
• hypothalamus
• immobilization stress
• small-animal PET

Acknowledgments

The authors thank Mr Chin-Chao Hsu and Mr Samuel Chen Leu for their technical help with the animal PET experiment. This work was supported by Grant-in-Aid for Young Scientists (KAKENHI 21791815) by the Ministry of Education, Culture, Sports, Science and Technology, an Open Research Center subsidy for the Research Center of Brain and Oral Science, Kanagawa Dental College of Japan, and by Neurobiology and Cognitive Science Center, National Taiwan University, and by a grant, NSC100-2311-B002-002-MY3 from National Science Council, Taiwan.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.