Abstract
Purpose: Pain is a physical stressor in humans and the common symptom for dental patients in clinical setting. However, the effects of pain as a stressor on the hypothalamic-pituitary-adrenocortical （HPA） axis have not yet been fully elucidated. In this study, plasma adrenocorticotropic hormone （ACTH） and corticosterone, in addition to corticotropin-releasing hormone （CRH） hnRNA and mRNA expression were examined to know how glossodynia by capsaicin injection into the tongue tip will influence on HPA axis.
Methods: Wistar rats （n=48） were divided into two groups of 24 animals each: a capsaicin-injected, a vehicle-injected. Rats were sacrificed at 5, 15, 30, or 60 min （n=6 each） after the injections into the left side of the tongue tip. Additionally, control-group rats （n=6） were sacrificed before any treatment （injection and anesthesia）. The blood was collected to measure plasma adrenocorticotropic hormone （ACTH） and corticosterone to make sure the hypothalamic-pituitary-adrenocortical （HPA） axis activation for stress response, and the tissues of hypothalamic paraventricular nucleus was used to detect CRH hnRNA and mRNA expression by quantitative real-time PCR analysis.
Results: ACTH secretion reached a peak at 30 min after glosso-injection prior to a gradual increase in plasma corticosterone. CRH hnRNA and mRNA expression was upregulated about 3-fold at 15 and 60 min, respectively, compared to control rats.
Conclusions: Glosso-injection of capsaicin can activate HPA axis through CRH gene expression.
