Fluoxetine enhances cell proliferation and prevents apoptosis in dentate gyrus of maternally separated rats

The mother-infant relationship is an instinctive phenomenon, and loss of maternal care in early life influences neonatal development, behavior and physiologic responses.(1,2) Furthermore, the early loss may affect the vulnerability of the infant to neuropsychiatric disorders, such as childhood anxiety disorders, personality disorders and depression, over its lifespan.(3,4) Fluoxetine is prescribed worldwide for depression and is often used in the treatment of childhood mental problems related to maternal separation or loss of maternal care.(5,6) In the present study, fluoxetine was administrated to rats with maternal separation to determine its effects on neuronal development, in particular with respect to cell proliferation and apoptosis in the dentate gyrus of the hippocampus. Rat pups were separated from their mothers and socially isolated on postnatal day 14 and were treated with fluoxetine (5 mg kg(-1)) and 5-bromo-2'-deoxyuridine (BrdU) (50 mg kg(-1)) for 7 days, after which immunohistochemistry and a terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining were carried out. In the pups with maternal separation treated with fluoxetine, the number of BrdU-positive cells was significantly increased and that of TUNEL-positive cells was significantly decreased in the dentate gyrus compared to pups with maternal separation that did not receive fluoxetine treatment. These findings indicate that fluoxetine affects new cell proliferation and apoptosis, and we propose that fluoxetine may be useful in the treatment of maternal separation-related diseases.