Inactivation of the prelimbic cortex enhances freezing induced by trimethylthiazoline, a component of fox feces.

Previous research has demonstrated that the rodent medial prefrontal cortex (mPFC) is critical for the expression of unconditioned defense behaviors. The prelimbic (PL) and infralimbic (IL) cortices comprise the majority of the mPFC, but the role of these regions in mediating unconditioned defense behaviors is not well understood. In order to address this, we temporarily inactivated the PL or IL and documented the effects of these manipulations on freezing induced by trimethylthiazoline (TMT), a component of fox feces, and center region avoidance in the open field (OF). PL inactivation enhanced TMT-induced freezing, but had no effect on OF behavior. IL inactivation had no effect on any behavioral measure. The results of this study are the first to demonstrate that the PL can have an inhibitory role with regard to unconditioned defense behavior. Further research is needed to define the parameters under which the PL inhibits unconditioned defense behavior.