光線藉由自主感光視網膜神經細胞調控小鼠社交記憶

Abstract

在哺乳動物之視網膜中，自主感光視神經細胞透過視黑質自身感光，並對於藍光最為敏感，其對於動物的生理時鐘，荷爾蒙恆定，瞳孔反射及認知行為當中，扮演相當重要的角色。在群居生活當中，社交行為扮演非常重要的一環，尤其對個體間至族群，社會結構的影響。而在過去人類研究當中，光線能影響我們在認知的行為表現，而究竟日常生活當中，環境的光線是如何影響我們的社交行為，其機制尚未明瞭，因此，我們結合不同基因轉殖鼠及行為學等實驗方式，探索其中的大腦神經迴路。從我們的研究結果發現，在接受一小時光照刺激後，小鼠的短期社交記憶表現受到影響，當部分自主感光視神經細胞亞型被去除時，小鼠的社交記憶形成則不受光線影響。此外，我們也發現神經性荷爾蒙催產激素可能參與其調控，催產素神經活性也可能間接的受到來自光線的刺激而改變其活性。綜合以上結果，自主感光視神經細胞及催產激素在光線調控小鼠社交記憶神經迴路中皆扮演舉足輕重的角色，然而，這些研究成果也為未來光線如何調控社交行為打開一道曙光。

In mammalian’s retinas, intrinsically photosensitive retinal ganglion cells (ipRGCs) can directly sense environmental light through photopigment melanopsin, which is most sensitive to blue light wavelength, independent of rods and cones. It has been shown that ipRGCs are important for circadian photoentrainment, pupil light reflex, sleep and mood regulation. In colony formation, social behavior plays a critical role between individuals, groups and social structure. It has been shown that light could influence the cognition functions in humans such as awareness and perception. However, the detail neural circuits for how external light influences our social behavior remains unclear. To test whether light could modulate social behavior, we combined different transgenic mouse lines and several behavior tests to investigate the neural circuits in the brain. Here we observed that one-hour light pulse could decrease sociosexual memory in mice. Genetically elimination of ipRGCs could block the light-dependent reduction of sociosexual memory. Moreover, application of oxytocin antagonist could also block the sociosexual memory, suggesting that oxytocin may involve in light-dependent modulation of sociosexual memory. In summary, it is likely that ipRGCs could transmit light information to modulate the release of oxytocin which influences sociosexual memory acquisition. These results provide novel direction to study how light influence the formation of sociosexual memory.