www.nature.com/npp ABSTRACTS COLLECTION ACNP 57th Annual Meeting: Panels, Mini-Panels and Study Groups Sponsorship Statement: Publication of this supplement is sponsored by the ACNP. Individual contributor disclosures may be found within the abstracts. Asterisks in the author lists indicate presenter of the abstract at the annual meeting. https://doi.org/10.1038/s41386-018-0265-8 Panel experiments were performed in 8-10-week-old male or female mice on a C57 background. 1. Dissecting the Contributions of Dopamine D1 and D2 Results: We observed dendritic atrophy in NAc D1-MSNs but Receptor-Expressing Neurons in Behaviors Dysregulated in not D2-MSNs in CSDS susceptible mice (P < 0.001). mRNAs of RhoA Neuropsychiatric Illness pathway molecules were significantly altered in D1-MSNs of CSDS susceptible mice (P < 0.05). Genetic overexpression of WT-RhoA in D1-MSNs induced dendritic atrophy and a susceptible outcome to 1.1 Dichotomous Structural Adaptations in Nucleus SSDS (P < 0.01), while DN-RhoA in D1-MSNs restored dendritic Accumbens Neuron Subtypes Underlie Stress Susceptibility complexity and caused a resilient outcome to CSDS (P < 0.05) compared to eYFP controls. RhoA (WT) in D1-MSNs caused reduced time grooming in splash test of female mice, reduced Mary Kay Lobo sucrose preference in male mice, and enhanced time immobile in forced swim test of both sexes (P < 0.05). Increased Egr3, the RhoA University of Maryland School of Medicine, Baltimore, Maryland, transcriptional regulator, in D2-MSNs promotes stress resiliency (P United States < 0.05) by preventing D2-MSN enhanced density of mushroom spines that occurs in stress susceptible mice (P < 0.01), without Background: Ventral striatum (nucleus accumbens-NAc) medium altering dendritic arbor. spiny neurons (MSNs) undergo structural plasticity after stress. Conclusions: D1-MSNs display dendritic atrophy and D2-MSNs However, there is little information into these adaptations, and the have enhanced dendritic spines in CSDS susceptible mice. underlying molecular mechanisms, in the two NAc MSN subtypes, Enhanced levels of the transcription factor Egr3 and its target those enriched in dopamine receptor 1 and 2 (D1-MSNs vs. D2- RhoA mediate D1-MSN dendritic atrophy and corresponding CSDS MSNs). Previously we showed that enhanced levels of the susceptible behavior. In contrast, enhanced Egr3 in D2-MSNs transcription factor, early growth response 3 (Egr3), caused blocks dendritic spine formation and causes stress resiliency. dendritic atrophy and depression-like behavior after 10-day Overall, we demonstrate dichotomous structural, molecular, and chronic social defeat stress (CSDS). We further showed that Egr3 behavioral outcomes to social defeat stress through NAc D1-MSNs transcriptionally regulates RhoA, a negative regulator of dendritic vs. D2-MSNs. complexity. However, it is unclear if RhoA or other structural Disclosure: Nothing to disclose. molecules regulate these morphological adaptations and whether these changes also occur in D2-MSNs. Methods: Using D1-Cre and A2A-Cre lines we examined dendritic complexity in NAc D1-MSNs vs. D2-MSNs of male mice 1.2 Cooperative Synaptic and Intrinsic Plasticity in Nucleus after CSDS. We used D1-Cre and A2A-Cre mice crossed to the Cre- Accumbens D1 Medium-Sized Spiny Neurons Promotes Stress- inducible RiboTag line to isolate and examine mRNAs of RhoA Induced Anhedonia and Behavioral Despair pathway molecules in MSN subtypes of stress susceptible mice and controls. We then infused Cre-inducible wildtype (WT)-RhoA, Hugo Tejeda dominate negative (DN)-RhoA, or eYFP adeno-associated virus (AAVs) into NAc of D1-Cre mice and subjected them to 1-day National Institute on Drug Abuse/National Institutes of Health, subthreshold (S)SDS or CSDS. To examine sex specific depression- Baltimore, Maryland, United States like effects of RhoA in D1-MSNs, unstressed male and female D1- Cre mice receiving RhoA AAVs into NAc underwent the splash test, sucrose preference, and forced swim test. Finally, to determine if Background: Stress is a powerful trigger of symptoms in Egr3, the upstream transcriptional regulator of RhoA, plays a role psychiatric disorders. Anhedonia and behavioral despair are in D2-MSNs in CSDS behavior and dendritic morphology we hallmark symptoms in a plethora of psychiatric disorders, infused Cre-inducible Egr3 AAV into NAc of A2A-Cre mice. Samples including depression. The nucleus accumbens (NAcc) is a brain sizes are 6-12 or 4-6 (pooled 4 mice; RiboTag experiments). region that has been widely implicated in mediating these Statistical analysis was performed with Two-way-ANOVAs. All symptoms. However, it is currently not clear how stress impacts © American College of Neuropsychopharmacology 2018 ACNP 57th Annual Meeting: Panels, Mini-Panels. S2 synaptic plasticity and intrinsic excitability in the NAcc, and how others sleep less. We recently showed that chronic social defeat they promote anhedonia and behavioral despair. stress (CSDS) in mice causes persistent alterations in sleep Methods: Utilizing a combination of ex-vivo electrophysiology, architecture, producing increases in time spent in paradoxical male and female transgenic mice, optogenetics, and viral- sleep (PS) as well as increases in the number of PS bouts that mediated gene transfer, we determined the impact of footshock persisted after cessation of the stressor. Previous work shows that stress on anhedonia and behavioral despair, synaptic plasticity of stress activates the transcription factor CREB and elevates target excitatory inputs to D1 and D2 MSNs, as well as changes in gene expression within the nucleus accumbens (NAc), and that intrinsic excitability. Furthermore, we determined whether synap- non-selective elevations in NAc CREB function produce tic and intrinsic excitability changes in D1 MSNs were sufficient depressive-like effects whereas disruptions in CREB function and necessary to drive stress-induced depressive behavior and produce antidepressant- and anxiolytic-like effects. Elevated NAc established that both synaptic and intrinsic changes cooperate to CREB function is associated with increased expression of promote this maladaptive behavior. dynorphin, an endogenous agonist at kappa-opioid receptors Results: In both male and female mice, footshock stress induces (KORs) that is co-expressed with GABA in dopamine D1 receptor- anhedonia and behavioral despair as assessed by the sucrose expressing medium spiny neurons (MSNs). Dynorphin, in turn, preference (n = 8 per group; t-test; t = 2.516(14); p = 0.0247) and produces feedback inhibition via KORs expressed on the cell forced swim tests (n = 7-8 per group; t-test; t = 3.488(13); p = bodies and terminals of ventral tegmental area (VTA) dopamine 0.004;), respectively. Ventral hippocampus (VH) inputs were neurons. Implicating dynorphin in the effects of CSDS on sleep, potentiated onto NAcc D1 MSNs (n = 9-13 per group; t-test; t administration of the KOR antagonist JDTic (10 mg/kg, IP) (20) = 3.47, p = 0.0024), but not D2 MSNs. Depotentiating VH mitigated CSDS-induced alterations in PS. Several lines of inputs to the NAcc rescued both stress-induced anhedonia (n = 9- evidence suggest that susceptibility to CSDS is accompanied by 13 per group; t-test; t(20) = 2.154, p = 0.0436) and behavioral reduced activity of D1-MSNs in the NAc; however, the ways in despair (n = 9-13 per group; t-test; t(20) = 3.47, p = 0.0024), which this neural population contributes to the persistent effects demonstrating that potentiation of VH inputs to D1 MSNs is of stress on sleep have not been thoroughly explored. Here we necessary for these effects. Intrinsic excitability was robustly examined how selective manipulation of D1-MSNs affects sleep enhanced in D1 MSNs from stressed mice (n = 22-32 per group; architecture, and the degree to which it can recapitulate effects of Two-way ANOVA; F(20, 730) = 6.39, p < 0.0001), while a modest CSDS on sleep-related endpoints. hypoexcitability was observed in D2 MSNs (n = 12-20 per group; Methods: We used a wireless EEG system that enables 1234567890();,: Two-way ANOVA; F(20, 470) = 2.03, p = 0.0056). Increased excit- continuous data collection in freely-moving male mice over a ability of D1 MSNs was mediated by a decrease in inwardly- period of weeks. To examine mechanisms of stress-induced sleep rectifying potassium currents mediated by KIR channels (n = 7-13 changes, we used viral vectors to express excitatory (hM3Dq) or per group; t-test; t(17) = 2.18, p = 0.043), which normally limit inhibitory (hM4Di) DREADDs (or mCherry control) in the NAc of excitability of MSNs. Overexpression of KIR channels selectively in mice expressing cre-recombinase in D1-MSNs (GENSAT FK-150). D1 MSNs rescued both stress-induced anhedonia (n = 6 per Mimicking the design of our previous CSDS study, after a 5-day group; t-test; t(10) = 6.542, p < 0.0001) and behavioral despair baseline, all mice received clozapine (0.3 mg/kg/day) in their (Two-way ANOVA; Treatment x Time Interaction; F(5, 70) = 2.701, drinking water for 10 days, followed by a 5-day washout. p = 0.0273). Furthermore, expression of dominant negative KIR Results: Chronic inhibition of D1-MSNs (via hM4Di) produced channels, which interfere with endogenous KIR function, was CSDS-like increases in PS time (F(2,24) = 12.87, p = 0.0002) with- sufficient to promote anhedonia and behavioral despair (n = 9 per out affecting slow wave sleep (SWS) or wakefulness (W) times. In group; t-test; t(16) = 2.707, p < 0.0001) in naïve animals. Lastly, we contrast, chronic activation of D1-MSNs (via hM3Dq) produced utilized novel disconnection procedures to demonstrate that decreases in PS time (F(2,20) = 4.662, p = 0.02), also without stress-induced depressive behaviors require both potentiation of affecting SWS or W times. These effects persisted following a 5- VH inputs to D1 MSNs and increased D1 MSN excitability. day DREADD ligand washout, suggesting that even transient Conclusions: Here we demonstrate that stress promotes activation or inhibition of this neuronal population can produce anhedonia and behavioral despair via cooperative increases in long-lasting effects on sleep.