The hypothalamic-pituitary-adrenal axis is part of a major homeostatic mechanism responsive to pain and stress. This study evaluated the corticosterone (CORT) and feeding responses to inflammation induced by bilateral complete Freund's adjuvant injection into the (TMJ) of the rat. Since CORT release is diurnal, adult male rats were divided into two experimental and two control groups: inflammation was induced in the experimental groups at either the beginning or end of the light phase; control groups were not injected. Food intake, corrected for spillage, was recorded over the course of the experiment. The rats were killed 48 hours after injection and non-stressed diurnal blood samples collected and assayed for CORT by radioimmunoassay. At the beginning of the light phase there was a significant elevation of plasma CORT in the experimental group when compared to controls (25 ng/ml vs 77.6 ng/ml, p< 0.05). However, at the end of the light phase the control group had a significantly higher concentration of CORT (162.1 ng/ml vs 89.3 ng/ml, p < 0.01). Food intake was significantly attenuated in the experimental groups over the measurement period. The data show that TMJ inflammation disrupts the diurnal release of CORT and decreases daily food intake.
