Endogenous Glucocorticoids in Traumatic Memory Extinction: Implications for PTSD

Abstract

Research on the physiological basis of PTSD has focused on the hypothalamic pituitary adrenal (HPA) axis, which releases hormones (glucocorticoids) that have profound effects on learning and memory in both health and disease. Due to ethical and practical limitations, research has focused on animal models of PTSD symptoms to understand the neural and endocrine mechanisms underlying the disorder. In this chapter, we discuss two animal models (fear conditioning and predator stress) which represent core symptoms of PTSD and review evidence suggesting that glucocorticoids facilitate extinction (learning of a less aversive stimulus-response relationship) of persistent fear memories and hyperarousal. The actions of glucocorticoids are discussed in the context of the neural circuitry underlying extinction.