CENTRAL EXPRESSION OF C-FOS PROTEIN AFTER PERIPHERAL NOXIOUS THERMAL-STIMULATION IN AWAKE RATS

This study applied immunohistochemistry method to examine the pattern of c-fos expression in the neuraxis following peripheral noxious therm al stimulation accomplished by immersion of tail of awake rat into hot water (50-degrees-C). In unstimulated control rats, no obvious baseli ne expression of c-fos protein was found except in nucleus paraventric ularis hypothalami and colliculus inferior, probably associated with r estraint-induced stress and auditory stimulus, respectively. Noxious t hermal stimulation resulted in the activation of c - fos expression , and bilateral increased nuclear immunostaining was counted in dorsal h orn of lumbar and sacral segments of spinal cord (laminae I, II), nucl eus raphe dorsalis, substantia grisea centralis (ventralis), nucleus p araventricularis thalami, nucleus anterior thalami, nucleus ventralis thalami, nucleus medialis thalami, nucleus reuniens, nucleus rhomboide us, nucleus habenulae lateralis, nucleus paraventricularis hypothalami , nucleus arcuatus, nucleus lateralis hypothalami, nucleus preopticus lateralis, nucleus septi lateralis, nucleus amygdala, nucleus striae t erminalis, nucleus tractus diagonalis, and cortex cerebri. The results demonstrated that peripheral noxious stimulation induced central c-fo s protein expression in a pattern of labeling nociresponsive cells.