The medial preoptic area (MPOA) is well known for its role in sexual and maternal behaviors. This region also plays an important role in affiliative social behaviors outside reproductive contexts. We recently demonstrated that the MPOA is a central nucleus in which opioids govern highly rewarding social play behavior in adolescent rats. However, the neural circuit mechanisms underlying MPOA-mediated social play remain largely unresolved. We hypothesized that the MPOA unites a complementary neural system through which social play induces reward via a projection to the ventral tegmental area (VTA) and reduces a negative affective state through a projection to the periaqueductal gray (PAG). To test whether the two projection pathways are activated in response to social play behavior, we combined retrograde tract tracing with immediate early gene (IEG) expression and immunofluorescent labeling to identify opioid-sensitive projection pathways from the MPOA to VTA and PAG that are activated after performance of social play. Retrograde tracer, fluoro-gold (FG), was microinjected into the VTA or PAG. IEG expression (i.e., Egr1) was assessed and triple immunofluorescent labeling for mu opioid receptor (MOR), Egr1, and FG in the MPOA was performed after social play. We revealed that play animals displayed an increase in neurons double labeled for Egr1 + FG and triple labeled for MOR + Egr1 + FG in the MPOA projecting to both the VTA and PAG when compared to no-play rats. The increased activation of projection neurons that express MORs from MPOA to VTA or PAG after social play suggests that opioids may act through these projection pathways to govern social play. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

中文翻译：

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幼年大鼠的社交游戏行为会激活内侧视前区及其向腹侧被盖区和导水管周围灰质的投射。

内侧视前区（MPOA）因其在性行为和产妇行为中的作用而闻名。该区域在生殖环境之外的亲和社会行为中也发挥着重要作用。我们最近证明，MPOA 是阿片类药物控制青春期大鼠高回报社交游戏行为的中心核。然而，MPOA 介导的社交游戏背后的神经回路机制在很大程度上仍未得到解决。我们假设 MPOA 联合了一个互补的神经系统，通过该系统，社交游戏通过投射到腹侧被盖区 (VTA) 来诱导奖励，并通过投射到导水管周围灰质 (PAG) 来减少负面情感状态。为了测试这两条投射通路是否因社交游戏行为而被激活，我们将逆行束追踪与即早期基因（IEG）表达和免疫荧光标记相结合，以识别从 MPOA 到 VTA 和 PAG 的阿片类药物敏感投射通路，这些通路在社交游戏行为后被激活。社交游戏的表现。将逆行示踪剂荧光金 (FG) 显微注射到 VTA 或 PAG 中。评估 IEG 表达（即 Egr1），并在社交游戏后对 MPOA 中的 mu 阿片受体 (MOR)、Egr1 和 FG 进行三重免疫荧光标记。我们发现，与不玩耍的大鼠相比，玩耍的动物在投射到 VTA 和 PAG 的 MPOA 中双标记 Egr1 + FG 和三标记 MOR + Egr1 + FG 的神经元有所增加。社交游戏后，表达从 MPOA 到 VTA 或 PAG 的 MOR 的投射神经元的激活增加，表明阿片类药物可能通过这些投射途径发挥作用来控制社交游戏。（PsycInfo 数据库记录 (c) 2023 APA，保留所有权利）。