Chronic social defeat downregulates the 5-HT1A receptor but not Freud-1 or NUDR in the rat prefrontal cortex

The serotonin 1A receptor (5-HT1A) and its associated transcriptional regulators, five prime repressor element under dual repression (Freud-1) and nuclear-deformed epidermal autoregulatory factor (NUDR/Deaf-1) have been previously found to be the repressors for 5-HT1A in the serotonergic raphe neurons, and are also altered in postmortem brains of individuals with major depressive disorder (MDD) and in rats exposed to chronic restraint stress. We sought to find out if rats exposed to chronic social defeat (CSD) stress also show altered expression of these genes. Adult male Wistar rats were exposed to CSD stress for four consecutive weeks following which they were sacrificed and gene expression assessed in the prefrontal cortex (PFC) by quantitative real-time polymerase chain reaction. While CSD had no significant effects on NUDR and Freud-1 mRNA levels, 5-HT1A mRNA levels were significantly downregulated in defeated animals. The data suggest that regulatory factors other than Freud-1 and NUDR may be involved in the regulation of 5-HT1A expression in PFC during CSD stress. Furthermore, decreased levels of 5-HT1A following social defeat in the PFC are consistent with human postmortem results for this receptor in major depression and demonstrate the possibility that this receptor is involved in the pathophysiology of depression and other stress related disorders.