, 2011a). IκK and its downstream targets IκB and phosphorylated IκB were upregulated in the NAc of susceptible mice following CSDS. Interestingly, activation of IκK–NFκB signaling promotes susceptibility

buy Erastin to CSDS by altering plasticity of glutamatergic synapses in the NAc. Strategies to blunt IκK–NFκB activation directly in NAc promote resilience. A subsequent study revealed that constitutive viral overexpression of IκK promotes baseline anxiety and depression-like behaviors in the open field and forced swim tests as well as social avoidance and anhedonic behavior in response to an acute social defeat stress (Christoffel et al., 2012). IκK expression induced the formation of immature spines (primarily thin spines) in mice exposed to acute social defeat stress. Again, spine density correlated significantly with social avoidance behavior, suggesting that IκK-dependent, stress-induced morphological changes may drive behavioral response to stress. Together, these data suggest a critical role for IκK–NFκB signaling in NAc in susceptibility vs. resilience to social stress. Future studies will be important to identify the upstream inflammatory signaling

pathways responsible for such effects. Much of our current knowledge regarding central mechanisms of resilience centers on mesocorticolimbic reward circuitry. Brain reward circuitry serves the adaptive purpose AG-14699 of focusing one’s attention on the acquisition of natural rewards to ultimately ensure survival (Russo and Nestler, 2013). Mesocorticolimbic circuitry comprises neurons from the medial prefrontal cortex (mPFC), hippocampus, NAc, amygdala, VTA, lateral hypothalamus, and

lateral habenula, ADP ribosylation factor among other brain regions (see Fig. 3). Collectively, these brain regions are involved in numerous psychological and cognitive processes that are impacted by stress and compromised in patients with depression or anxiety (Christoffel et al., 2011b). Connections between mesocorticolimbic regions are dense and often complex. Here, we will focus primarily on the most well characterized connections, those of the VTA–NAc reward circuit. Dopaminergic neurons of the VTA project onto GABAergic medium spiny neurons (MSNs) of the NAc, a structure within the ventral striatum. VTA neurons release dopamine in response to reward-related stimuli to initiate consumption and sometimes also in response to aversive stimuli. The NAc sends reciprocal connections back to the VTA via two pathways—the direct pathway, via D1-type MSNs; and the indirect pathway, via D2-type MSNs, which innervate GABAergic interneurons in the ventral pallidum that in turn synapse onto VTA neurons.