Kim, Janice J (2014-12). Reversible Inactivation of the Bed Nucleus of the Stria Terminalis Blocks Reinstatement But Not Renewal of Extinguished Fear. Master's Thesis.
The bed nucleus of the stria terminalis (BNST) is thought to be involved in the expression of fear to shock-associated contexts, but not to discrete conditional stimuli (CSs) paired with shock. Because context plays an important role in the extinction and relapse of fear, we sought to examine the contribution of the BNST to two different relapse phenomena: renewal and reinstatement. In the renewal experiment, male Long-Evans rats received 5 tone-shock trials for conditioning in "context A"; 24 hours later they received 45 tone-alone (extinction) trials in either "context B" or "context C". Ten minutes prior to a retrieval test (5 tone-alone trials), rats were infused with either selective agonist for GABAA receptors, muscimol or vehicle in the BNST. In the reinstatement experiment, rats underwent a similar procedure, but were presented with an unsignaled 'reminder' shock in the extinction context to reinstate fear. As before, we examined the influence of muscimol inactivation of the BNST during a retrieval testing 24-hours after the reinstatement shock. In the reinstatement test, rats with muscimol infusion showed significantly less freezing than did rats with vehicle infusion. In contrast, BNST inactivation did not attenuate the renewal of fear to an extinguished CS outside the extinction context. These data indicate that the BNST is involved in forms of fear relapse that depend on direct associations of the test context with an aversive US.