title: Increased depression-like behaviors with dysfunctions in the stress axis and the reward center by free access to highly palatable food.
abstract: This study was conducted to examine the behavioral consequences of unlimited consumption of highly palatable food (HPF) and investigate its underlying neural mechanisms. Male Sprague-Dawley rats had free access to chocolate cookie rich in fat (HPF) in addition to ad libitum chow and the control group received chow only. Rats were subjected to behavioral tests during the 2nd week of food condition; i.e. ambulatory activity test on the 8th, elevated plus maze test (EPM) on the 10th and forced swim test (FST) on the 14th day of food condition. After 8 days of food condition, another group of rats were placed in a restraint box and tail bloods were collected at 0, 20, 60, and 120 time points during 2h of restraint period, used for the plasma corticosterone assay. At the end of restraint session, rats were sacrificed and the tissue sections of the nucleus accumbens (NAc) were processed for c-Fos immunohistochemistry. Ambulatory activities and the scores of EPM were not significantly affected by unlimited cookie consumption. However, immobility duration during FST was increased, and swim decreased, in the rats received free cookie access compared with control rats. Stress-induced corticosterone increase was exaggerated in cookie-fed rats, while the stress-induced c-Fos expression in the NAc was blunted, compared to control rats. Results suggest that free access to HPF may lead to the development of depression-like behaviors in rats, likely in relation with dysfunctions in the hypothalamic-pituitary-adrenal axis and the reward center.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Dental Research Institute, Seoul National University School of Dentistry, Seoul 110-768, Republic of Korea.
authors.forename: E
authors.initials: E
authors.lastname: Park
authors.affiliation: Department of Oral and Maxillofacial Surgery, Dental Research Institute, Seoul National University School of Dentistry, Seoul 110-768, Republic of Korea.
authors.forename: J Y
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, Dental Research Institute, Seoul National University School of Dentistry, Seoul 110-768, Republic of Korea. Electronic address: leejongh@snu.ac.kr.
authors.forename: J-H
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Oral and Maxillofacial Surgery, Dental Research Institute, Seoul National University School of Dentistry, Seoul 110-768, Republic of Korea. Electronic address: jwjahng@snu.ac.kr.
authors.forename: J W
authors.initials: JW
authors.lastname: Jahng
mesh_terms: D000821:Animal Feed; D000818:Animals; D002099:Cacao; D003345:Corticosterone / Q000097:blood; D003866:Depressive Disorder / Q000503:physiopathology*; D004032:Diet; D004435:Eating; D005106:Exploratory Behavior / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D018782:Maze Learning / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D009714:Nucleus Accumbens / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000503:physiopathology*; D013550:Swimming / Q000502:physiology; D015430:Weight Gain
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D003345:Corticosterone
keywords: corticosterone; food intake; nucleus accumbens; stress