Regional differentiation of the medial prefrontal cortex in regulating adaptive responses to acute emotional stress.

The medial prefrontal cortex (mPFC) is an important neural substrate for integrating cognitive-affective information and regulating the hypothalamo-pituitary-adrenal (HPA) axis response to emotional stress. mPFC modulation of stress responses is effected in part via the paraventricular hypothalamic nucleus (PVH), which houses both autonomic (sympathoadrenal) and neuroendocrine (HPA) effector mechanisms. Although the weight of evidence suggests that mPFC influences on stress-related PVH outputs are inhibitory, discordant findings have been reported, and such work has tended to treat this cortical region as a unitary structure. Here we compared the effects of lesions of the dorsal versus ventral aspects of mPFC, centered in the prelimbic and infralimbic fields, respectively, on acute restraint stress-induced activation of PVH cell groups mediating autonomic and neuroendocrine responses. Lesions to the dorsal mPFC enhanced restraint-induced Fos and corticotropin-releasing factor (CRF) mRNA expression in the neurosecretory region of PVH. Ablation of the ventral mPFC decreased stress-induced Fos protein and CRF mRNA expression in this compartment but increased Fos induction in PVH regions involved in central autonomic control. Repetition of the experiments in rats bearing retrograde tracer deposits to label PVH-autonomic projections confirmed that ventral mPFC lesions selectively increased stress-induced Fos expression in identified preautonomic neurons. Finally, hormonal indices of HPA activation in response to acute stress were augmented after dorsal mPFC lesions and attenuated after ventral mPFC lesions. These results suggest that dorsal and ventral aspects of the mPFC differentially regulate neuroendocrine and autonomic PVH outputs in response to emotional stress.