Oxytocin regulates social behaviours, pair bonding and hippocampal neurogenesis but most studies have used adult males. Our study investigated the effects of oxytocin on social investigation and adult hippocampal neurogenesis in male and female rats. Oxytocin has poor penetration of the blood-brain barrier, therefore we tested a nanoparticle drug, TRIOZAN™ (Ovensa Inc.), which permits greater blood-brain-barrier penetration. Adult male and female rats were injected daily (i.p.) for 10 days with either: oxytocin in PBS (0.5 or 1.0 mg/kg), oxytocin in TRIOZAN™ (0.5 or 1.0 mg/kg), or vehicle (PBS) and tested for social investigation. Oxytocin decreased body mass and increased social investigation and number of oxytocin-immunoreactive cells in the supraoptic nucleus (SON) of the hypothalamus in male rats only. In both sexes, oxytocin decreased the number of immature neurons (doublecortin+ cells) in the ventral hippocampus and reduced plasma 17β-estradiol levels in a dose- and delivery-dependent way. Oxytocin in TRIOZAN™ reduced "sedation" observed post-injection and increased certain central effects (oxytocin levels in the hypothalamus and neurogenesis in the ventral hippocampus) relative to oxytocin in PBS, indicating that the nanoparticle may be used as an alternative brain delivery system. We showed that oxytocin has sex-specific effects on social investigation, body mass, "sedation", and the oxytocin system. In contrast, similar effects were observed in both sexes in neurogenesis and plasma 17β-estradiol. Our work suggests that sex differences in oxytocin regulation of brain endpoints is region-specific (hypothalamus versus hippocampus) and that oxytocin does not promote social investigation in females.

中文翻译：

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催产素对成年大鼠的社交行为和下丘脑催产素免疫反应性细胞具有性别特异性影响，但对海马神经发生没有影响。

催产素调节社交行为，配对和海马神经发生，但是大多数研究都使用成年男性。我们的研究调查了催产素对雌雄大鼠的社会调查和成年海马神经发生的影响。催产素对血脑屏障的渗透性较差，因此我们测试了一种纳米颗粒药物TRIOZAN™（Ovensa Inc.），该药物可实现更大的血脑屏障渗透性。每天（ip）给成年雄性和雌性大鼠注射（ip）10天，其中包括：催产素的PBS（0.5或1.0 mg / kg），催产素的TRIOZAN™（0.5或1.0 mg / kg）或赋形剂（PBS）并测试其社会调查。催产素降低了体重，增加了社会调查，并且仅在雄性大鼠下丘脑的视上核（SON）中产生了催产素免疫反应性细胞。无论男女 催产素以剂量和递送依赖性方式减少腹侧海马中未成熟神经元（双皮质素+细胞）的数量，并降低血浆17β-雌二醇水平。相对于PBS中的催产素，TRIOZAN™中的催产素减少了注射后观察到的“镇静”，并增加了某些中枢效应（下丘脑中的催产素水平和腹侧海马神经发生），这表明纳米粒子可以用作替代的脑部输送系统。我们证明了催产素对社会调查，体重，“镇静”和催产素系统具有性别特异性影响。相比之下，在神经发生和血浆17β-雌二醇中都观察到了相似的作用。