Reproductive experience facilitates recovery from kainic acid-induced neural insult in female Long-Evans rats

The hormones of pregnancy and lactation (e.g., estrogen, progesterone, and oxytocin) have been shown to modulate learning, memory, and the restructuring of brain areas not traditionally associated with maternal behavior. Given the impact of reproductive experience on plasticity of brain areas such as the hippocampus, kainic acid (KA) was used in the current study to induce hippocampal-specific neurotoxic insult in adult multiparous and virgin Long-Evans rats. In Experiment I, Fluoro-Jade B, an indicant of degenerating cells, revealed significant neuronal damage in KA-treated hippocampi at 16 h post-injection in both maternal and virgin rats. In Experiment II, maternal and virgin rats were assessed in spatial and novel object preference tasks to determine the effects of KA on subsequent behavioral and cognitive responses. Twenty-four hours post injection, saline maternal animals exhibited superior memory in a spatial task. Further, maternal saline-injected rats were more similar to maternal KA-injected rats than both the virgin groups. Forty-eight hours following the KA or saline injection, compared to virgins, maternal animals demonstrated enhanced memory in the novel object memory test, regardless of type of injection. Further, neurobiological assessments in Experiment II indicated that virgin KA exposed rats had significantly more glial fibrillary acidic protein (GFAP)-immunoreactivity in the hippocampus, suggesting that they were in an earlier stage of neural recovery compared to maternal animals or, alternatively, may have exhibited more trauma than maternal animals. Together, these data suggest that the previously reported plasticity of the maternal brain may facilitate neural and behavioral recovery from neural insults.