Dopamine error signal to actively cope with lack of expected reward

目標に向けて努力し続けられる脳の仕組みを解明 --期待外れを乗り越えるためのドーパミン機能--. 京都大学プレスリリース. 2023-03-13.Dope defense against disappointment: Neurons in rats increase dopamine immediately after setbacks. 京都大学プレスリリース. 2023-06-20.To obtain more of a particular uncertain reward, animals must learn to actively overcome the lack of reward and adjust behavior to obtain it again. The neural mechanisms underlying such coping with reward omission remain unclear. Here, we developed a task in rats to monitor active behavioral switch toward the next reward after no reward. We found that some dopamine neurons in the ventral tegmental area exhibited increased responses to unexpected reward omission and decreased responses to unexpected reward, following the opposite responses of the well-known dopamine neurons that signal reward prediction error (RPE). The dopamine increase reflected in the nucleus accumbens correlated with behavioral adjustment to actively overcome unexpected no reward. We propose that these responses signal error to actively cope with lack of expected reward. The dopamine error signal thus cooperates with the RPE signal, enabling adaptive and robust pursuit of uncertain reward to ultimately obtain more reward

Protective Effect of Meretrix meretrix Oligopeptides on High-Fat-Diet-Induced Non-Alcoholic Fatty Liver Disease in Mice

The present study investigated the effects of MMO (Meretrix meretrix oligopeptides) on mice fed a high-fat diet. Mice were fed either a normal control diet (NC) or a high-fat diet (HFD) without or with MMO (50 mg/kg or 250 mg/kg) for four weeks. Levels of ALT, AST, liver tissue GSH-Px, and SOD activities, MDA levels were measured using commercially available kits; HE staining was performed to analyze pathologic changes of the liver; a TEM assay was performed to measure the ultrastructural alterations of the mitochondria, and Western blotting was performed to detect the expression of gene proteins related to lipid metabolism, inflammation, and liver apoptosis. After six weeks, body weight, ALT, AST, and MDA levels were significantly increased, and GSH-Px levels and SOD activities were significantly decreased in the HFD control group compared with the NC group. Consumption of the HFD compared with the NC caused fatty liver abnormal mitochondria with loss of cristae, intramitochondrial granules, and a swollen and rarefied matrix. Administration of MMO significantly decreased body weight gain, and ALT, AST, and MDA levels; increased SOD activity and GSH-Px levels; alleviated fatty liver steatosis; decreased the early apoptosis population; downregulated SREBP-1c, Bax, Caspase-9, Caspase-3, TNF-α, and NF-κB protein levels; and upregulated PPAR-α, Bcl-2, and AMPK-α, compared with the HFD control group. MMO exhibited protective effects in mice with NAFLD by regulating the NF-κB anti-inflammation signaling pathways to inhibit inflammation, regulate AMPK-α, PPAR-α and SREBP-1c to improve lipid metabolism disorder, and regulate Bcl-2/Bax anti-apoptosis signaling pathways to prevent liver cell apoptosis. These results suggest that dietary supplementation with MMO ameliorates high-fat-diet-induced NAFLD

Neural control of affiliative touch in prosocial interaction

The ability to help and care for others fosters social cohesiveness and is vital to the physical and emotional well-being of social species, including humans1-3. Affiliative social touch, such as allogrooming (grooming behaviour directed towards another individual), is a major type of prosocial behaviour that provides comfort to others1-6. Affiliative touch serves to establish and strengthen social bonds between animals and can help to console distressed conspecifics. However, the neural circuits that promote prosocial affiliative touch have remained unclear. Here we show that mice exhibit affiliative allogrooming behaviour towards distressed partners, providing a consoling effect. The increase in allogrooming occurs in response to different types of stressors and can be elicited by olfactory cues from distressed individuals. Using microendoscopic calcium imaging, we find that neural activity in the medial amygdala (MeA) responds differentially to naive and distressed conspecifics and encodes allogrooming behaviour. Through intersectional functional manipulations, we establish a direct causal role of the MeA in controlling affiliative allogrooming and identify a select, tachykinin-expressing subpopulation of MeA GABAergic (γ-aminobutyric-acid-expressing) neurons that promote this behaviour through their projections to the medial preoptic area. Together, our study demonstrates that mice display prosocial comforting behaviour and reveals a neural circuit mechanism that underlies the encoding and control of affiliative touch during prosocial interactions

Inhibition of Prostate Cancer DU-145 Cells Proliferation by Anthopleura anjunae Oligopeptide (YVPGP) via PI3K/AKT/mTOR Signaling Pathway

We investigated the antitumor mechanism of Anthopleura anjunae oligopeptide (AAP-H, YVPGP) in prostate cancer DU-145 cells in vitro and in vivo. Results indicated that AAP-H was nontoxic and exhibited antitumor activities. Cell cycle analysis indicated that AAP-H may arrest DU-145 cells in the S phase. The role of the phosphatidylinositol 3-kinase/protein kinase B/mammalian rapamycin target protein (PI3K/AKT/mTOR) signaling pathway in the antitumor mechanism of APP-H was investigated. Results showed that AAP-H treatment led to dose-dependent reduction in the levels of p-AKT (Ser473), p-PI3K (p85), and p-mTOR (Ser2448), whereas t-AKT and t-PI3K levels remained unaltered compared to the untreated DU-145 cells. Inhibition of PI3K/AKT/mTOR signaling pathway in the DU-145 cells by employing inhibitor LY294002 (10 μM) or rapamycin (20 nM) effectively attenuated AAP-H-induced phosphorylation of AKT and mTOR. At the same time, inhibitor addition further elevated AAP-H-induced cleaved-caspase-3 levels. Furthermore, the effect of AAP-H on tumor growth and the role of the PI3K/AKT/mTOR signaling pathway in nude mouse model were also investigated. Immunohistochemical analysis showed that activated AKT, PI3K, and mTOR levels were reduced in DU-145 xenografts. Western blotting showed that AAP-H treatment resulted in dose-dependent reduction in p-AKT (Ser473), p-PI3K (p85), and p-mTOR (Ser2448) levels, whereas t-AKT and t-PI3K levels remained unaltered. Similarly, Bcl-xL levels decreased, whereas that of Bax increased after AAP-H treatment. AAP-H also increased initiator (caspase 8 and 9) and executor caspase (caspase 3 and 7) levels. Therefore, the antitumor mechanism of APP-H on DU-145 cells may involve regulation of the PI3K/AKT/mTOR signaling pathway, which eventually promotes apoptosis via mitochondrial and death receptor pathways. Thus, the hydrophobic oligopeptide (YVPGP) can be developed as an adjuvant for the prevention or treatment of prostate cancer in the future

Midbrain Dopamine Controls Anxiety-like Behavior by Engaging Unique Interpeduncular Nucleus Microcircuitry

BACKGROUND: Dopamine (DA) is hypothesized to modulate anxiety-like behavior, although the precise role of DA in anxiety behaviors and the complete anxiety network in the brain have yet to be elucidated. Recent data indicate that dopaminergic projections from the ventral tegmental area (VTA) innervate the interpeduncular nucleus (IPN), but how the IPN responds to DA and what role this circuit plays in anxiety-like behavior are unknown. METHODS: We expressed a genetically encoded G protein-coupled receptor activation-based DA sensor in mouse midbrain to detect DA in IPN slices using fluorescence imaging combined with pharmacology. Next, we selectively inhibited or activated VTA--\u3eIPN DAergic inputs via optogenetics during anxiety-like behavior. We used a biophysical approach to characterize DA effects on neural IPN circuits. Site-directed pharmacology was used to test if DA receptors in the IPN can regulate anxiety-like behavior. RESULTS: DA was detected in mouse IPN slices. Silencing/activating VTA--\u3eIPN DAergic inputs oppositely modulated anxiety-like behavior. Two neuronal populations in the ventral IPN (vIPN) responded to DA via D1 receptors (D1Rs). vIPN neurons were controlled by a small population of D1R neurons in the caudal IPN that directly respond to VTA DAergic terminal stimulation and innervate the vIPN. IPN infusion of a D1R agonist and antagonist bidirectionally controlled anxiety-like behavior. CONCLUSIONS: VTA DA engages D1R-expressing neurons in the caudal IPN that innervate vIPN, thereby amplifying the VTA DA signal to modulate anxiety-like behavior. These data identify a DAergic circuit that mediates anxiety-like behavior through unique IPN microcircuitry