Netrin-1 mediates stress-induced plasticity of adult pyramidal neurons

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During development, the guidance cue receptor, DCC, guides growing axons towards Netrin-1-secreting targets. However, DCC receptors also dictate the fine organization of synaptic connectivity once growing axons have reached their final targets, by controlling axon arborization, dendritic growth and synapse formation. These post-axonal pathfinding processes continue to occur in adulthood and are intimately involved in experience-induced synaptic plasticity. Recent work from our laboratory shows that exposure to chronic social defeat stress in adult male mice results in upregulation of DCC receptor expression in medial prefrontal cortex (mPFC) pyramidal neurons and that this causes susceptibility to develop social avoidance, anhedonia, and anxiety-like behaviors. Knocking out DCC receptors in these neurons prior to stress exposure induces resilience to these effects. How DCC-mediated Netrin-1 signaling in adult pyramidal neurons mediate stress-induced behavioral changes remains to be determined. This proposal is aimed at addressing this question by investigating whether (i) DCC-dependent reorganization of dendritic structure/organization and of spine morphology are involved and (ii) specific neuronal circuits are affected, namely mPFC projections to the nucleus accumbens and/or mPFC projections to the amygdala, two limbic regions involved in motivation and processing of emotional information. To test these ideas, we will continue using a model of chronic social stress in adult male mice and a battery of behavioral tests to measure social interaction, motivation and reward. We will combine these behavioral methods with state-of-the-art anatomical, molecular, and neural recording strategies. In these experiments we will also implement a model of social stress defeat in female mice to begin addressing similar questions in females. This research will provide information, for the first time, about the role of guidance cues in stress-induced plasticity. It will also identify the neural circuitries that are involved in this process.