Differential involvement of amygdalar NMDA receptors in variants of adolescent contextual fear conditioning
Date
2018
Authors
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Publisher
University of Delaware
Abstract
The context preexposure facilitation effect (CPFE) is a variant of contextual fear conditioning that consists of three distinct phases in which learning the context (preexposure), the context-shock association (training), and retrieval of the context-shock association (testing) are separated by 24 hours. In contrast, in standard contextual fear conditioning (sCFC), learning of the context and formation of the context-shock association occur in the same training session. In adult rats, disrupting basolateral amygdala (BLA) activity or plasticity during training on sCFC impairs both post-shock and retention freezing (Maren et al., 1996). This manipulation on the training day of the CPFE disrupts retention freezing but effects on post-shock freezing are unknown (Matus-Amat et. al., 2007). Experiment 1 extends this literature from adult to adolescent rats and to the role of BLA in post-shock freezing during the CPFE. Experiment 2 directly compares the role of plasticity within the BLA on training day of sCFC and CPFE. Experiment 3 examines the role of BLA plasticity on retention of contextual fear when acquisition is not tested. In the first experiment, intra-BLA infusions of muscimol prior to the training day of the CPFE disrupted both post-shock and retention freezing in postnatal day (PD) 31-33 rats. In the second two experiments, intra-BLA infusions of APV prior to training day of sCFC disrupts retention but not post-shock freezing, while infusions of APV prior to training of the CPFE disrupt both post-shock and retention freezing. Our findings suggest that the BLA plays a different role in the CPFE vs. sCFC. Its role in the CPFE is similar in both adolescent and adult rats, while the role of the BLA in post-shock freezing during sCFC may differ across age or across studies that employ different procedures or parameters.
Description
Keywords
Biological sciences, Amygdala, Contextual fear conditioning, Hippocampus, Medial prefrontal cortex, NMDA receptor, Ontogeny