Figure 3.

Intra-LC infusions of enkephalin block stress-induced freezing. The experimental timeline is shown in (A). Rats were habituated to handling by the experimenter for 3 days but were naïve to the behavioral apparatus when testing began. Rats that received saline infusions into LC froze in the OFT significantly more than control rats that received saline infusions, and more than control or stressed rats that received enkephalin infusions. Stressed rats that received enkephalin infusions did not freeze more than control rats that received enkephalin infusions (B). A representative photomicrograph showing bilateral cannulae placement within LC is shown in the bottom right. * p < 0.05; ** p < 0.01.