Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90033, USA.
Department of Integrative Anatomical Sciences, Keck School of Medicine of the University of Southern California, Los Angeles, CA 90033, USA; Department of Pharmaceutical Biosciences, Uppsala University, Sweden.
Horm Behav. 2017 Nov;96:122-129. doi: 10.1016/j.yhbeh.2017.09.011. Epub 2017 Sep 24.
Prolactin (PRL) and oxytocin (OT) are pituitary hormones essential for lactation, but also promote sexual behavior. OT stimulates social behaviors, such as recognition, approach, and learning, but less is known about PRL in these behaviors. Since PRL and OT have complementary functions in reproduction, we hypothesized that PRL increases social recognition, approach, and learning. Male Long-Evans rats received ovine PRL (oPRL; 0.5, 2.0 or 5.0mg/kg), the PRL antagonist bromocriptine (0.1, 3.0 or 5.0mg/kg) or saline 20 mins before testing for recognition of familiar vs. unfamiliar stimulus males. Saline controls preferred the unfamiliar male (p<0.05), while bromocriptine blocked this preference. oPRL did not increase preference. To measure social approach, we determined if PRL restores approach 2h after defeat by an aggressive male. Defeated rats avoided the aggressive male. 2mg/kg oPRL, before or after defeat, restored approach towards the aggressive male (p<0.05). In non-defeated rats, oPRL or 3mg/kg bromocriptine had no effect. To determine if PRL increases social learning, we tested social transmission of food preference. Rats choose between two unfamiliar flavors, one of which they have previously been exposed to through interaction with a demonstrator rat. Vehicle controls preferred chow with the demonstrated flavor over the novel flavor. oPRL-treated rats were similar. Bromocriptine-treated rats failed to show a preference. When tested one week later, only oPRL-treated rats preferred the demonstrated flavor. The results suggest that PRL is required for social recognition and learning, and that increasing PRL enhances social memory and approach, similar to OT.
催乳素（PRL）和催产素（OT）是泌乳所必需的垂体激素，但也促进性行为。OT 刺激社交行为，如识别、接近和学习，但对 PRL 在这些行为中的作用知之甚少。由于 PRL 和 OT 在生殖中具有互补功能，我们假设 PRL 会增加社交识别、接近和学习。雄性长耳大仓鼠在接受绵羊 PRL（oPRL；0.5、2.0 或 5.0mg/kg）、PRL 拮抗剂溴隐亭（0.1、3.0 或 5.0mg/kg）或生理盐水 20 分钟后，进行识别熟悉与陌生刺激雄性的测试。生理盐水对照更喜欢陌生雄性（p<0.05），而溴隐亭则阻止了这种偏好。oPRL 并未增加偏好。为了测量社交接近，我们确定 PRL 是否可以在被攻击性雄性击败后 2 小时恢复接近。被击败的大鼠回避攻击性雄性。2mg/kg 的 oPRL，在被击败之前或之后，恢复了对攻击性雄性的接近（p<0.05）。在未被击败的大鼠中，oPRL 或 3mg/kg 的溴隐亭没有影响。为了确定 PRL 是否增加社交学习，我们测试了食物偏好的社交传递。大鼠在两种不熟悉的口味之间进行选择，其中一种口味是通过与示教大鼠的互动之前接触过的。载体对照更喜欢有示范风味的食物而不是新颖风味。oPRL 处理的大鼠则类似。溴隐亭处理的大鼠未能表现出偏好。一周后进行测试时，只有 oPRL 处理的大鼠更喜欢示范风味。结果表明，PRL 是社交识别和学习所必需的，增加 PRL 会增强社交记忆和接近，类似于 OT。
