Maternal deprivation regulates serotonin 1A and 2A receptors in the infant rat

Several studies have demonstrated that 5-HT1A and 5-HT2A receptors are altered in rat brain following chronic stress. While this is true in the adult animal, this may be different in the developing animal, which has a limited corticosterone response to acute challenges between days 3 and 14 of life.

We investigated the effect of maternal deprivation on 5-HT2A and 5-HT1A receptor mRNA levels in the developing brain. In situ hybridization was used to quantify gene expression in rat pups at three ages: 6, 9, and 12 days old. In each age group, half were maternally deprived for 24 h and half were kept with their mothers. Maternally deprived animals showed elevated ACTH and corticosterone plasma levels when compared to NDEP animals, significantly elevated 5-HT1A mRNA levels in the CA1 hippocampal region and, significantly elevated 5-HT2A mRNA levels in the parietal cortex. No changes were observed in 5-HT1A or 5-HT-transporter mRNA levels in the dorsal raphe. Our results indicate that post-synaptic 5-HT receptors in the developing hippocampus and cortex are sensitive to maternal deprivation. Because hippocampal 5-HT1A gene expressions are known to decrease in the adult animal after chronic glucocorticoid elevation, this data also suggests that other mechanisms, perhaps central, predominate during development.