Roles of corticosterone in formalin-induced conditioned place aversion in rats

Glucocorticoid hormones have been shown to contribute to many cognitive functions, such as depressions, learning and memory, and abnormal glucocorticoid secretion results in functional changes in prefrontal cortex and amygdala. In the present study, we used the conditioned place aversion (CPA) paradigm to investigate the role of corticosterone (CORT) in the negative affective component of chemical somatic pain induced by intraplantar injection of formalin into male adult Long-Evan rats. Five percent of formalin produced acute biphasic nociceptive behaviors, including flinching and licking of hindpaw, and CPA. Intraplantar formalin induced CPA was abolished by bilateral adrenalectomy and the impairment of CPA can be restored by the CORT treatment. However, the adrenalectomy failed to affect the formalin-produced acute nociceptive behaviors. Therefore, data from the present study suggest that CORT secretion by the adrenal cortex may play a role in chemical somatic noxious stimuli-induced avoidance learning and aversive memory, but not sensory discrimination of noxious stimulation.