Neuroscience Program, Michigan State University, East Lansing, MI, USA.
Eur J Neurosci. 2013 Feb;37(3):457-68. doi: 10.1111/ejn.12058. Epub 2012 Nov 22.
A successful transition from childhood to adulthood requires adolescent maturation of social information processing. The neurobiological underpinnings of this maturational process remain elusive. This research employed the male Syrian hamster as a tractable animal model for investigating the neural circuitry involved in this critical transition. In this species, adult and juvenile males display different behavioral and neural responses to vaginal secretions, which contain pheromones essential for expression of sexual behavior in adulthood. These studies tested the hypothesis that vaginal secretions acquire positive valence over adolescent development via remodeling of neural circuits underlying sexual reward. Sexually naïve adult, but not juvenile, hamsters showed a conditioned place preference for vaginal secretions. Differences in behavioral response to vaginal secretions between juveniles and adults correlated with a difference in the vaginal secretion-induced neural activation pattern in mesocorticolimbic reward circuitry. Fos immunoreactivity increased in response to vaginal secretions in the medial amygdala and ventral tegmental dopaminergic cells of both juvenile and adult males. However, only in adults was there a Fos response to vaginal secretions in non-dopaminergic cells in interfascicular ventral tegmental area, nucleus accumbens core and infralimbic medial prefrontal cortex. These results demonstrate that a socially relevant chemosensory stimulus acquires the status of an unconditioned reward during adolescence, and that this adolescent gain in social reward is correlated with experience-independent engagement of specific cell groups in reward circuitry.
从儿童期到成年期的成功过渡需要青少年社交信息处理能力的成熟。这一成熟过程的神经生物学基础仍难以捉摸。这项研究采用雄性叙利亚仓鼠作为一种易于处理的动物模型，来研究参与这一关键过渡的神经回路。在这种物种中，成年和幼年雄性对阴道分泌物表现出不同的行为和神经反应，阴道分泌物中含有成年期性行为表达所必需的信息素。这些研究检验了这样一个假设，即阴道分泌物通过重塑性奖励相关的神经回路，在青少年发育过程中获得积极的效价。性未成熟的成年仓鼠，但不是幼年仓鼠，对阴道分泌物表现出条件性位置偏好。青少年和成年仓鼠对阴道分泌物的行为反应差异与中脑边缘奖赏回路中阴道分泌物诱导的神经激活模式差异相关。阴道分泌物会引起内侧杏仁核和腹侧被盖区多巴胺能细胞中的 Fos 免疫反应增加，这在幼年和成年雄性中都有发生。然而，只有在成年雄性中，阴道分泌物会引起非多巴胺能细胞的 Fos 反应，这些非多巴胺能细胞位于束间腹侧被盖区、伏隔核核心和边缘前脑内侧前额叶皮质。这些结果表明，一种与社交相关的化学感觉刺激在青少年时期获得了无条件奖励的地位，而这种青少年时期社会奖励的增加与奖赏回路中特定细胞群的经验独立参与有关。
