Plasticity in the maternal circuit: effects of maternal experience on Fos-Lir in hypothalamic, limbic, and cortical structures in the postpartum rat.

To determine what brain sites are activated during the acquisition and retention of a maternal experience in postpartum rats, 3 studies examined the number of cells showing Fos-like immunoreactivity (Fos-lir) in brains following reexposure to pups and pup-associated cues in maternally experienced and inexperienced rats. Day 1 postpartum rats were given a 2- or 4-hr interactive experience with pups and then reexposed to pups in a perforated box, or to a neutral stimulus (perforated box only) 4 or 10 days later. At the end of the test phase, brains were prepared for immunohistochemical detection of Fos-lir. The brain sites showing the most consistent difference between experienced and inexperienced rats were the medical preoptic area, the basolateral amygdala, the parietal cortex, and the prefrontal cortex.