Neonatal handling on the first postnatal day leads to increased maternal behavior and fos levels in the brain of the newborn rat.

In the present work we employed Fos expression, an index of neuronal activity, to identify brain areas activated by a single exposure to "neonatal handling" on postnatal Day 1. Eight hours following "handling" there was an increase in the number of Fos positive cells in the hippocampus, the parietal and occipital cortex. We also recorded maternal behavior during the 8 hr following "handling." "Handled" pups received increased maternal licking during the 4 hr following the end of "handling." Furthermore, the number of Fos positive cells detected in each of the three brain areas 8 hr following "handling" was positively correlated with the amount of licking up to 8 hr following "handling." These results indicate that the increased maternal care could underlie the handling-induced increase in Fos. The Fos protein, acting as a transcription factor, controls the expression of downstream genes, whose products may mediate the effects of "neonatal handling" on the developing rat brain.