OPRK1 and Anxiety: To determine whether inactivation of Pdyn expression from a diversity of inputs to the CeA is sufficient to phenocopy the inactivation of Oprk1 on anxiety-like behavior and conditioned threat discrimination, we injected Pdynlox/lox and control (Pdyn+/+) mice with the retrograde transducing virus CAV2 containing an expression cassette for Cre recombinase (CAV2-Cre).