Induction of galanin after chronic sertraline treatment in mouse ventral dentate gyrus.

A number of studies implicate neuroplasticity in the therapeutic mechanisms of antidepressants, specifically neuroplasticity in the dentate gyrus of the hippocampal formation. The dorsal hippocampal region in rodents is preferentially involved in spatial learning and memory, while the ventral hippocampal region plays a more important role in stress, emotion, and affective behaviors. These findings led us to investigate behavioral changes and gene expression changes in the ventral and dorsal dentate gyrus differentially after chronic treatment in mice with the antidepressant sertraline. Four-week treatment with sertraline significantly decreased immobility in the modified forced swim test, a behavioral test for assessing antidepressant-like effects in rodents. In the novelty-suppressed feeding test, performance of which is affected by functional changes in the dentate gyrus, sertraline treatment significantly decreased latency to feed. Next, we examined the expression of several neuroplasticity-related genes (those for Notch receptors, basic helix-loop-helix transcription factors and related factors, SoxC transcription factors, and glial-related genes) by real-time RT-PCR in the ventral and dorsal dentate gyrus of mice after the sertraline treatment. The gene encoding the neuropeptide galanin was significantly induced in only ventral dentate gyrus, not in dorsal dentate gyrus. These results suggest that sertraline-related galanin induction in ventral dentate gyrus may play an important role in therapeutic mechanisms for depression.