Involvement of subdivisions of the medial prefrontal cortex in learned cardiac adjustments in rabbits.

Electrical stimulation of area 24 and area 32 of the medial prefrontal cortex (mPFC) in rabbits elicited increases in respiration rate and decreases in heart rate (HR) and blood pressure. However, stimulation in area 25 elicited pressor responses and a biphasic HR response consisting of an initial HR increase followed by an HR decrease. Administration of an alpha-adrenergic receptor antagonist eliminated the pressor response and bradycardiac response produced by area 25 stimulation but it had no effect on the bradycardia elicited by stimulation of area 24 or area 32. Lesions centered on area 32 of the mPFC greatly attenuated the conditioned bradycardiac response elicited by paired tone and paraorbital shock presentations. Lesions of area 24 produced a decrease in discrimination between a reinforced conditioned stimulus and a nonreinforced conditioned stimulus but had no effect on the magnitude of the conditioned response. Area 25 lesions had no effect on any aspect of conditioned responding.