Ontrollable versus Uncontrollable Stressors I-directionally Modulate Conditioned but Not Nnate Fear

bstract—Fear conditioning and fear extinction play key oles in the development and treatment of anxiety-related isorders, yet there is little information concerning experienial variables that modulate these processes. Here we examned the impact of exposure to a stressor in a different envionment on subsequent fear conditioning and extinction, and hether the degree of behavioral control that the subject has ver the stressor is of importance. Rats received a session of ither escapable (controllable) tail shock (ES), yoked inesapable (uncontrollable) tail shock (IS), or control treatment home cage, HC) 7 days before fear conditioning in which a one and foot shock were paired. Conditioning was measured 4 h later. In a second experiment rats received ES, IS or HC 4 h after contextual fear conditioning. Extinction then ocurred every day beginning 7 days later until a criterion was eached. Spontaneous recovery of fear was assessed 14 ays after extinction. IS potentiated fear conditioning when iven before fear conditioning, and potentiated fear respondng during extinction when given after conditioning. Imporantly, ES potently interfered with later fear conditioning, dereased fear responding during fear extinction, and prevented pontaneous recovery of fear. Additionally, we examined if the ctivation of the ventral medial prefrontal cortex (mPFCv) by S is critical for the protective effects of ES on later fear conitioning. Inactivation of the mPFCv with muscimol at the time f the initial experience with control prevented ES-induced reuctions in later contextual and auditory fear conditioning. Finally, we explored if the protective effects of ES extended o an unconditioned fear stimulus, ferret odor. Unlike condiioned fear, prior ES increased the fear response to ferret odor o the same degree as did IS. © 2007 IBRO. Published by lsevier Ltd. All rights reserved.