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 d ecreases in heart rate (HR) and blood pressure. However, stimulation i n area 25 elicited presser responses and a biphasic HR response consis ting of an initial HR increase followed by an HR decrease. Administrat ion of an a-adrenergic receptor antagonist eliminated the presser resp onse 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 t he conditioned bradycardiac response elicited by paired tone and parao rbital shock presentations. Lesions of area 24 produced a decrease in discrimination between a reinforced conditioned stimulus and a nonrein forced conditioned stimulus but had no effect on the magnitude of the conditioned response. Area 25 lesions had no effect on any aspect of c onditioned responding.