Lesions of the medial prefrontal cortex enhance the early phase of psychogenic fever to unexpected sucrose concentration reductions, promote recovery from negative contrast and enhance spontaneous recovery of sucrose-entrained anticipatory activity

• Published in: Neuroscience 2008-06, Vol.153 (4), p.901-917
• Main Authors: Pecoraro, N, de Jong, H, Ginsberg, A.B, Dallman, M.F
• Format: Article
• Language: English
• Subjects: Adrenocorticotropic Hormone - blood; Analysis of Variance; Animals; Behavior, Animal; Biological and medical sciences; Body Temperature - physiology; Body Weight; Conditioning, Operant; Corticosterone - blood; Dose-Response Relationship, Drug; Eating - physiology; expectancy; extinction; Fever - etiology; Food Deprivation; food entrainment; Fundamental and applied biological sciences. Psychology; Male; medial prefrontal cortex; Motor Activity - physiology; Neurology; Prefrontal Cortex - injuries; Prefrontal Cortex - physiology; psychogenic fever; Rats; Rats, Wistar; Recovery of Function - physiology; Restraint, Physical - methods; Stress, Psychological - blood; Stress, Psychological - etiology; Stress, Psychological - physiopathology; successive negative contrast; Sucrose - administration & dosage; Time Factors; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2008.03.043

Abstract Two groups of rats, one bearing bilateral excitotoxic lesions of the medial prefrontal cortex (mPFC) and one sham-lesioned group, were run in a successive negative contrast paradigm. Both groups had telemeters implanted to monitor core temperature and activity. After ad libitum baseline and food restriction to 85% body weights, rats received a sucrose solution once daily for 5 min and 30 s at 10:30 h. They received their preshift 32% sucrose solution for 14 days followed by a sucrose concentration reduction (downshift) to 4% sucrose for 12 days. Rats were then upshifted to 32% for six additional days before being downshifted to 4% for the next 6 days. There were no differences in intake of the 32% sucrose during the preshift. All rats showed profound suppression of intake upon the shift to 4% sucrose. On the first day of the unexpected 4% sucrose, lesioned rats showed an enhanced psychogenic fever compared with Shams, whereas on the second day of 4% sucrose they showed an impaired ability to blunt that fever compared with Shams. In addition, lesioned rats showed greater rates of recovery and asymptotic drinking of the subsequent 4% sucrose solution than Shams, indicating impairments in the encoding or retrieval of the shift. In addition, lesioned rats showed enhanced entrainment to the 32% sucrose meals, normal damping of anticipation, and enhanced spontaneous recovery of anticipatory thermal responses to the calorically impoverished 4% solutions. These failures to inhibit responding point to a failure in interference learning in rats bearing lesions of the mPFC.