Abstract
Corticotrophin-releasing factor (CRF), a key regulator of the hypothalamic-pituitary axis, is expressed in the central nucleus of the amygdala (CeA) and its expression is upregulated in stress-related disorders. We investigated here the effect of noxious colorectal distension (CRD) on the expression of CRF in the CeA of conscious and unconscious rats. Adult male rats with or without general anesthesia were exposed to visceral pain induced by CRD for 5 min; this procedure was repeated 3 times with 1 min resting after each distension. The rats were sacrificed and sections of the CeA were immunostained for CRF as an indicator for anxiety response, and for phosphorylated extracellular signal-regulated kinase (p-ERK) as a marker for pain-specific activation of neurons; sections of lumbosacral spinal cord were immunostained for c-Fos as a marker for activation of spinal neurons. CRD elicited a significant increase in the expression of CRF and p-ERK in the CeA and of c-Fos in the spinal cord. General anesthesia attenuated the increase in CRF and p-ERK in the CeA, but did not affect the expression of spinal c-Fos. These results suggest that conscious recognition of pain at higher brain centers is an important determinant of CRF expression in the CeA.