title: Neonatal glucocorticoid treatment increased depression-like behaviour in adult rats.
abstract: Synthetic glucocorticoid dexamethasone (DEX) is frequently used as a therapeutic agent to lessen the morbidity of chronic lung disease in premature infants. Previous studies suggested that neonatal DEX treatment altered brain development and cognitive function. It has been recognized that the amygdala is involved in emotional processes and also a critical site of neuronal plasticity for fear conditioning. Little is known about the possible long-term adverse effect of neonatal DEX treatment on amygdala function. The present study was aimed to evaluate the possible effect of neonatal DEX treatment on the synaptic function of amygdala in adult rats. Newborn Wistar rats were subjected to subcutaneous tapering-dose injections of DEX (0.5, 0.3 and 0.1 mg/kg) from post-natal day one to three, PN1-PN3. Animals were then subjected to a forced swimming test (FST) and electrophysiological recording aged eight weeks. The results of the FST showed neonatal DEX treatment increased depression-like behaviour in adulthood. After acute stress evoking, the percentage of time spent free floating is significantly increased in the DEX treated group compared with the control animals. Furthermore, neonatal DEX treatment elevated long-term potentiation (LTP) response and the phosphorylation level of MAPK in the lateral nucleus of amygdala (LA). Intracerebroventricular infusion of the MAPK inhibitor, PD98059, showed significant rescue effects including reduced depression-like behaviour and restoration of LTP to within normal range. In conclusion, our results suggested that MAPK signalling cascade in the LA plays an important role in the adverse effect of neonatal DEX treatment on amygdala function, which may result in adverse consequences in adult age, such as the enhancement of susceptibility for a depressive disorder in later life.
authors.affiliation: Department of Life Science,National Taiwan Normal University,Taipei,Taiwan.
authors.forename: Meng-Chang
authors.initials: MC
authors.lastname: Ko
authors.affiliation: Department of Life Science,National Taiwan Normal University,Taipei,Taiwan.
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Hung
authors.affiliation: Graduate Institute of Oncology,National Taiwan University,Taipei,Taiwan.
authors.forename: Pei-Yin
authors.initials: PY
authors.lastname: Ho
authors.affiliation: Department of Biochemical Science and Technology,National Chia-Yi University,Chia-Yi,Taiwan.
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Yang
authors.affiliation: Department of Life Science,National Taiwan Normal University,Taipei,Taiwan.
authors.forename: Kwok-Tung
authors.initials: KT
authors.lastname: Lu
mesh_terms: D000679:Amygdala / Q000187:drug effects* / Q000254:growth & development* / Q000503:physiopathology; D000818:Animals; D000831:Animals, Newborn; D000928:Antidepressive Agents / Q000494:pharmacology; D003866:Depressive Disorder / Q000139:chemically induced* / Q000188:drug therapy / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000494:pharmacology; D005938:Glucocorticoids / Q000633:toxicity*; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011897:Random Allocation; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000503:physiopathology; D046509:Tissue Culture Techniques
chemical_list: D000928:Antidepressive Agents; D005419:Flavonoids; D005938:Glucocorticoids; D047428:Protein Kinase Inhibitors; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one