Maras Pamela M, Petrulis Aras
Department of Psychology, Center for Behavioral Neuroscience, Georgia State University, PO Box 3966, Atlanta, GA 30302-3966, USA.
Eur J Neurosci. 2006 Dec;24(12):3541-52. doi: 10.1111/j.1460-9568.2006.05216.x.
In rodent species, such as the Syrian hamster, the expression of sexual preference requires neural integration of social chemosensory signals and steroid hormone cues. Although anatomical data suggest that separate pathways within the nervous system process these two signals, the functional significance of this separation is not well understood. Specifically, within the medial amygdala, the anterior region (MEa) receives input from the olfactory bulbs and other chemosensory areas, whereas the posterodorsal region (MEpd) contains a dense population of steroid receptors and receives less substantial chemosensory input. Consequently, the MEa may subserve a primarily discriminative function, whereas the MEpd may mediate the permissive effects of sex steroids on sexual preference. To test these hypotheses, we measured preference and attraction to female and male odors in males with lesions of either the MEa or MEpd. In Experiment 1, lesions of either region eliminated opposite-sex odor preferences. Importantly, MEpd-lesioned males displayed decreased attraction toward female odors, suggesting decreased sexual motivation. In contrast, MEa-lesioned males displayed high levels of investigation of both male and female odors, suggesting an inability to categorize the relevance of the odor stimuli. In Experiment 2, we verified that both MEa- and MEpd-lesioned males could discriminate between female and male odors, thereby eliminating the possibility that the observed lack of preference reflected a sensory deficit. Taken together, these results suggest that both the MEa and MEpd are critical for the expression of opposite-sex odor preference, although they appear to mediate distinct aspects of this behavior.
在啮齿动物物种中，如叙利亚仓鼠，性偏好的表达需要社会化学感觉信号和类固醇激素线索的神经整合。尽管解剖学数据表明神经系统内的不同通路处理这两种信号，但这种分离的功能意义尚不清楚。具体而言，在内侧杏仁核中，前部区域（MEa）接收来自嗅球和其他化学感觉区域的输入，而后背侧区域（MEpd）含有密集的类固醇受体群体，并且接收较少的化学感觉输入。因此，MEa可能主要发挥辨别功能，而MEpd可能介导性类固醇对性偏好的允许作用。为了验证这些假设，我们测量了MEa或MEpd损伤的雄性对雌性和雄性气味的偏好和吸引力。在实验1中，任一区域的损伤都消除了对异性气味的偏好。重要的是，MEpd损伤的雄性对雌性气味的吸引力降低，表明性动机下降。相比之下，MEa损伤的雄性对雄性和雌性气味都表现出高水平的探究，表明无法对气味刺激的相关性进行分类。在实验2中，我们证实MEa和MEpd损伤的雄性都能够区分雌性和雄性气味，从而排除了观察到的偏好缺乏反映感觉缺陷的可能性。综上所述，这些结果表明MEa和MEpd对于异性气味偏好的表达都至关重要，尽管它们似乎介导了这种行为的不同方面。
