Lonstein Joseph S, Linning-Duffy Katrina, Yan Lily
Neuroscience Program & Department of Psychology, Michigan State University, East Lansing, MI, United States.
Front Behav Neurosci. 2019 Apr 12;13:72. doi: 10.3389/fnbeh.2019.00072. eCollection 2019.
Seasonal affective disorder (SAD) involves a number of psychological and behavioral impairments that emerge during the low daytime light intensity associated with winter, but which remit during the high daytime light intensity associated with summer. One symptom frequently reported by SAD patients is reduced sexual interest and activity, but the endocrine and neural bases of this particular impairment during low daylight intensity is unknown. Using a diurnal laboratory rodent, the Nile grass rat (), we determined how chronic housing under a 12:12 h day/night cycle involving dim low-intensity daylight (50 lux) or bright high-intensity daylight (1,000 lux) affects males' copulatory behavior, reproductive organ weight, and circulating testosterone. We also examined the expression of mRNAs for the aromatase enzyme, estrogen receptor 1 (ESR1), and androgen receptor (AR) in the medial preoptic area (mPOA; brain site involved in the sensory and hormonal control of copulation), and mRNAs for the dopamine (DA) D1 and D2 receptors in both the mPOA and nucleus accumbens (NAC; brain site involved in stimulus salience and motivation to respond to reward). Compared to male grass rats housed in high-intensity daylight, males in low-intensity daylight displayed fewer mounts and intromissions when interacting with females, but the groups did not differ in their testes or seminal vesicle weights, or in their circulating levels of testosterone. Males in low-intensity daylight unexpectedly had higher ESR1, AR and D1 receptor mRNA in the mPOA, but did not differ from high-intensity daylight males in D1 or D2 mRNA expression in the NAC. Reminiscent of humans with SAD, dim winter-like daylight intensity impairs aspects of sexual behavior in a male diurnal rodent. This effect is not due to reduced circulating testosterone and is associated with upregulation of mPOA steroid and DA receptors that may help maintain some sexual motivation and behavior under winter-like lighting conditions.
季节性情感障碍（SAD）涉及一些心理和行为障碍，这些障碍在与冬季相关的白天低光照强度期间出现，但在与夏季相关的白天高光照强度期间缓解。SAD患者经常报告的一种症状是性兴趣和性行为减少，但在低日照强度下这种特殊障碍的内分泌和神经基础尚不清楚。我们使用一种昼夜活动的实验啮齿动物——尼罗草鼠，确定了在12:12小时昼夜循环下长期饲养，包括昏暗的低强度日光（50勒克斯）或明亮的高强度日光（1000勒克斯），如何影响雄性的交配行为、生殖器官重量和循环睾酮水平。我们还检测了内侧视前区（mPOA，参与交配的感觉和激素控制的脑区）中芳香化酶、雌激素受体1（ESR1）和雄激素受体（AR）的mRNA表达，以及mPOA和伏隔核（NAC，参与刺激显著性和对奖励做出反应的动机的脑区）中多巴胺（DA）D1和D2受体的mRNA表达。与饲养在高强度日光下的雄性草鼠相比，饲养在低强度日光下的雄性在与雌性互动时表现出较少的爬跨和插入行为，但两组在睾丸或精囊重量以及循环睾酮水平上没有差异。出乎意料的是，饲养在低强度日光下的雄性在mPOA中ESR1、AR和D1受体mRNA水平较高，但在NAC中D1或D2 mRNA表达与饲养在高强度日光下的雄性没有差异。与患有SAD的人类相似，类似冬季的昏暗日光强度会损害雄性昼夜活动啮齿动物的性行为。这种影响不是由于循环睾酮减少，而是与mPOA类固醇和DA受体的上调有关，这可能有助于在类似冬季的光照条件下维持一些性动机和行为。
