Neural systems underlying important behaviors are usually highly conserved across species. The medial preoptic area (MPOA) has been demonstrated to play a crucial role in reward associated with affiliative, nonsexual, social communication in songbirds. However, the role of MPOA in affiliative, rewarding social behaviors (eg, social play behavior) in mammals remains largely unknown. Here we applied our insights from songbirds to rats to determine whether opioids in the MPOA govern social play behavior in rats. Using an immediate early gene (ie, Egr1, early growth response 1) expression approach, we identified increased numbers of Egr1‐labeled cells in the MPOA after social play in adolescent male rats. We also demonstrated that cells expressing mu opioid receptors (MORs, gene name Oprm1) in the MPOA displayed increased Egr1 expression when adolescent rats were engaged in social play using double immunofluorescence labeling of MOR and Egr1. Furthermore, using short hairpin RNA‐mediated gene silencing we revealed that knockdown of Oprm1 in the MPOA reduced the number of total play bouts and the frequency of pouncing. Last, RNA sequencing differential gene expression analysis identified genes involved in neuronal signaling with altered expression after Oprm1 knockdown, and identified Egr1 as potentially a key modulator for Oprm1 in the regulation of social play behavior. Altogether, these results show that the MPOA is involved in social play behavior in adolescent male rats and support the hypothesis that the MPOA is part of a conserved neural circuit across vertebrates in which opioids act to govern affiliative, intrinsically rewarded social behaviors.

中文翻译：

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视前内侧区域的阿片类阿片受体控制着青春期雄性大鼠的社交行为。

构成重要行为的神经系统通常在物种间高度保守。事实表明，内侧视前区（MPOA）在与鸣禽的隶属性，非性社会交往相关的奖励中起关键作用。然而，在哺乳动物中，MPOA在亲和性，奖励性社会行为（例如，社会游戏行为）中的作用仍然未知。在这里，我们将从鸣禽到老鼠的洞察力应用于确定MPOA中的阿片类药物是否支配着老鼠的社交行为。使用立即早期基因（即Egr1，早期生长反应1）表达方法，我们确定了成年雄性大鼠社交活动后MPOA中Egr1标记的细胞数量增加。我们还证明了表达mu阿片受体（MORs，当青春期大鼠使用MOR和Egr1双重免疫荧光标记进行社交活动时，MPOA中的基因名称Oprm1）显示Egr1表达增加。此外，使用短发夹RNA介导的基因沉默，我们揭示了MPOA中Oprm1的敲低减少了总比赛次数和突跳次数。最后，RNA测序差异基因表达分析确定了参与Oprm1敲除后表达改变的神经元信号涉及的基因，并确定Egr1是Oprm1在调节社交行为中的潜在关键调控因子。总而言之，这些结果表明MPOA参与了青春期雄性大鼠的社交活动行为，并支持了MPOA是整个脊椎动物保守神经回路（其中阿片类药物起支配性作用）的一部分的假设。