Morphine- and foot shock-responsive neuronal ensembles in the VTA possess different connectivity and biased GPCR signaling pathway.

Background: Neurons in the ventral tegmental area (VTA) are sensitive to stress and their maladaptation have been implicated in the psychiatric disorders such as anxiety and addiction, etc. The cellular properties of the VTA neurons in response to different stressors related to different emotional processing remain to be investigated. Methods: By combining immediate early gene (IEG)-dependent labeling, rabies virus tracing, ensemble-specific transcriptomic analysis and fiber photometry recording in the VTA of male mice, the spatial distribution, brain-wide connectivity and cellular signaling pathways in the VTA neuronal ensembles in response to morphine (Mor-Ens) or foot shock (Shock-Ens) stimuli were investigated. Results: Optogenetic activation of the Mor-Ens drove approach behavior, whereas chemogenetic activation of the Shock-Ens increased the anxiety level in mice. Mor-Ens were clustered and enriched in the ventral VTA, contained a higher proportion of dopaminergic neurons, received more inputs from the dorsal medial striatum and the medial hypothalamic zone, and exhibited greater axonal arborization in the zona incerta and ventral pallidum. Whereas Shock-Ens were more dispersed, contained a higher proportion of GABAergic neurons, and received more inputs from the ventral pallidum and the lateral hypothalamic area. The downstream targets of the G protein and ß-arrestin pathways, PLCß3 and phosphorylated AKT1Thr308, were relatively enriched in the Mor-Ens and Shock-Ens, respectively. Cariprazine, the G-protein-biased agonist for the dopamine D2 receptor, increased the response of Mor-Ens to sucrose water and decreased the anxiety-like behavior during morphine withdrawal, whereas the ß-arrestin-biased agonist UNC9994 decreased the response of Shock-Ens to tail suspension. Conclusions: Taken together, these findings reveal the heterogeneous connectivity and signaling pathways of the VTA neurons in response to morphine and foot shock, providing new insights for development of specific interventions for psychiatric disorders caused by various stressors associated with different VTA neuronal functions.

O-GlcNAcylation mediates H2O2-induced apoptosis through regulation of STAT3 and FOXO1.

The O-linked-ß-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation) is a critical post-translational modification that couples the external stimuli to intracellular signal transduction networks. However, the critical protein targets of O-GlcNAcylation in oxidative stress-induced apoptosis remain to be elucidated. Here, we show that treatment with H2O2 inhibited O-GlcNAcylation, impaired cell viability, increased the cleaved caspase 3 and accelerated apoptosis of neuroblastoma N2a cells. The O-GlcNAc transferase (OGT) inhibitor OSMI-1 or the O-GlcNAcase (OGA) inhibitor Thiamet-G enhanced or inhibited H2O2-induced apoptosis, respectively. The total and phosphorylated protein levels, as well as the promoter activities of signal transducer and activator of transcription factor 3 (STAT3) and Forkhead box protein O 1 (FOXO1) were suppressed by OSMI-1. In contrast, overexpressing OGT or treating with Thiamet-G increased the total protein levels of STAT3 and FOXO1. Overexpression of STAT3 or FOXO1 abolished OSMI-1-induced apoptosis. Whereas the anti-apoptotic effect of OGT and Thiamet-G in H2O2-treated cells was abolished by either downregulating the expression or activity of endogenous STAT3 or FOXO1. These results suggest that STAT3 or FOXO1 are the potential targets of O-GlcNAcylation involved in the H2O2-induced apoptosis of N2a cells.

[Sucrose reward promotes rats' motivation for cocaine].

Caloric diet, such as fat and sugar intake, has rewarding effects, and has been indicated to affect the responses to addictive substances in animal experiments. However, the possible association between sucrose reward and the motivation for addictive drugs remains to be elucidated. Thus, we carried out behavioral tests after sucrose self-administration training to determine the effects of sucrose experience on rats' motivation for cocaine, locomotor sensitivity to cocaine, basal locomotor activity, anxiety level, and associative learning ability. The sucrose-experienced (sucrose) group exhibited higher lever press, cocaine infusion and break point, as well as upshift of cocaine dose-response curve in cocaine self-administration test, as compared with the control (chow) group. Additionally, despite similar locomotor activity in open field test and comparable score in cocaine-induced conditioned place preference, the sucrose group showed higher cocaine-induced locomotor sensitivity as compared with the chow group. The anxiety level and the performance in vocal-cue induced fear memory were similar between these two groups in elevated plus maze and fear conditioning tests, respectively. Taken together, our work indicates that sucrose experience promotes the rats' motivation for cocaine.