Differential Effects of Voluntary Ethanol Consumption on Dopamine Output in the Nucleus Accumbens Shell of Roman High- and Low-Avoidance Rats: A Behavioral and Brain Microdialysis Study

The Roman high(RHA) and low-Avoidance (RLA) rats were selectively bred for rapid vs poor acquisition of two-way active avoidance behavior. These lines differ in numerous behavioral traits, with RLA rats being more fearful/anxious than RHA rats, and the latter being novelty-seekers and showing larger intake of, and preference for, addictive substances including ethanol (ETH). Moreover, several differences in central dopaminergic, serotonergic, and GABAergic functions have been reported in these two lines. Since those neural systems are involved in the regulation of ETH consumption, it was considered of interest to investigate: 1) the differences in ETH intake and preference between RHA and RLA rats, 2) the effects of ETH on DA release in the shell of the nucleus accumbens (AcbSh) using brain microdialysis. ETH solutions of increasing concentrations (2% - 10%) were presented on alternate days in a free choice with water. To examine ETH intake and preference stability, animals were subsequently switched to daily presentations of 10% ETH for 10 consecutive days. RHA rats consumed significantly larger amounts of ETH and displayed higher ETH preference than did RLA rats throughout the acquisition and maintenance phases. Following chronic exposure to ETH the animals were habituated to a restricted access to ETH schedule (2% ETH, 2 h per day × 4 days) before surgical implantation of a dialysis probe in the AcbSh. Under these experimental conditions, voluntary ETH intake (2%, 1 h, p.o.) produced a significant increase in accumbal DA output in RHA rats but not in their RLA counterparts. Finally, the i.p. administration of ETH (0.25 g/kg) to na?ve Roman rats produced a significant increment in accumbal DA output only in RHA rats. These results indicate that the mesolimbic dopaminergic system of RHA rats is more responsive to the effects of ETH than that of RLA rats.

Sequential Recommendation via Cross-Domain Novelty Seeking Trait Mining

Transfer learning has attracted a large amount of interest and research in last decades, and some effort has been made to build more precise recommendation systems. Most previous transfer recommendation systems assume that the target domain shares the same/similar rating patterns with the auxiliary source domain, which is used to improve the recommendation performance. However, almost all existing transfer learning work does not consider the characteristics of sequential data. In this paper, we study the new cross-domain recommendation scenario by mining novelty-seeking trait. Recent studies in psychology suggest that novelty-seeking trait is highly related to consumer behavior, which has a profound business impact on online recommendation. Previous work performed on only one single target domain may not fully characterize users' novelty-seeking trait well due to the data scarcity and sparsity, leading to the poor recommendation performance. Along this line, we propose a new cross-domain novelty-seeking trait mining model (CDNST for short) to improve the sequential recommendation performance by transferring the knowledge from auxiliary source domain. We conduct systematic experiments on three domain datasets crawled from Douban to demonstrate the effectiveness of our proposed model. Moreover, we analyze the directed influence of the temporal property at the source and target domains in detail.

Toll-Like Receptor 4 Deficiency Causes Reduced Exploratory Behavior in Mice Under Approach-Avoidance Conflict

Abnormal approach-avoidance behavior has been linked to deficits in the mesolimbic dopamine（DA）system of the brain. Recently, increasing evidence has indicated that toll-like receptor 4（TLR4）, an important pattern-recognition receptor in the innate immune system,can be directly activated by substances of abuse, resulting in an increase of the extracellular DA level in the nucleus accumbens. We thus hypothesized that TLR4-dependent signaling might regulate approach-avoidance behavior. To test this hypothesis, we compared the novelty-seeking and social interaction behaviors of TLR4-deficient（TLR4^（-/-））and wild-type（WT） mice in an approach-avoidance conflict situation in which the positive motivation to explore a novel object or interact with an unfamiliar mouse was counteracted by the negative motivation to hide in exposed,large spaces. We found that TLR4^（-/-）mice exhibitedreduced novelty-seeking and social interaction in the large open spaces. In less stressful test apparatuses similar in size to the mouse cage, however, TLR4^（-/-）mice performed normally in both novelty-seeking and social interaction tests. The reduced exploratory behaviors under approachavoidance conflict were not due to a high anxiety level or an enhanced fear response in the TLR4^（-/-）mice, as these mice showed normal anxiety and fear responses in the open field and passive avoidance tests, respectively. Importantly,the novelty-seeking behavior in the large open field induced a higher level of c-Fos activation in the nucleus accumbens shell（NAc Sh） in TLR4^（-/-）mice than in WT mice. Partially inactivating the NAc Sh via infusion of GABA receptor agonists restored the novelty-seeking behavior of TLR4^（-/-）mice. These data suggested that TLR4 is crucial for positive motivational behavior under approach-avoidance conflict. TLR4-dependent activation of neurons in the NAc Sh may contribute to this phenomenon.