Centre for Biological Timing, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.
BMC Biol. 2023 Aug 21;21(1):178. doi: 10.1186/s12915-023-01663-6.
Animal survival depends on the ability to adjust behaviour according to environmental conditions. The circadian system plays a key role in this capability, with diel changes in the quantity (irradiance) and spectral content ('colour') of ambient illumination providing signals of time-of-day that regulate the timing of rest and activity. Light also exerts much more immediate effects on behaviour, however, that are equally important in shaping daily activity patterns. Hence, nocturnal mammals will actively avoid light and dramatically reduce their activity when light cannot be avoided. The sensory mechanisms underlying these acute effects of light are incompletely understood, particularly the importance of colour.
To define sensory mechanisms controlling mouse behaviour, we used photoreceptor-isolating stimuli and mice with altered cone spectral sensitivity (Opn1mwR), lacking melanopsin (Opn1mwR; Opn4) or cone phototransduction (Cnga3) in assays of light-avoidance and activity suppression. In addition to roles for melanopsin-dependent irradiance signals, we find a major influence of spectral content in both cases. Hence, remarkably, selective increases in S-cone irradiance (producing a blue-shift in spectrum replicating twilight) drive light-seeking behaviour and promote activity. These effects are opposed by signals from longer-wavelength sensitive cones, indicating a true spectrally-opponent mechanism. Using c-Fos-mapping and multielectrode electrophysiology, we further show these effects are associated with a selective cone-opponent modulation of neural activity in the key brain site implicated in acute effects of light on behaviour, the subparaventricular zone.
Collectively, these data reveal a mechanism whereby blue-shifts in the spectrum of environmental illumination, such as during twilight, promote mouse exploratory behaviour.
动物的生存依赖于根据环境条件调整行为的能力。昼夜节律系统在这一能力中起着关键作用，环境光照的数量（辐照度）和光谱含量（“颜色”）的日变化提供了时间的信号，调节休息和活动的时间。然而，光对行为也有更直接的影响，这些影响同样对塑造日常活动模式很重要。因此，夜间活动的哺乳动物会主动避开光，并在无法避免光时大大减少活动。这些急性光效应的感觉机制尚不完全清楚，尤其是颜色的重要性。
为了定义控制小鼠行为的感觉机制，我们使用了分离感光器的刺激和具有改变的视锥光谱敏感性（Opn1mwR）的小鼠，在回避光和抑制活动的测定中缺乏视黑质（Opn1mwR; Opn4）或视锥光转导（Cnga3）。除了视黑质依赖性辐照度信号的作用外，我们还发现光谱含量在这两种情况下都有主要影响。因此，令人惊讶的是，选择性增加 S-锥体辐照度（产生类似于曙光的光谱蓝移）会驱动光寻求行为并促进活动。这些效应与长波长敏感锥体的信号相反，表明存在真正的光谱对立机制。使用 c-Fos 映射和多电极电生理学，我们进一步表明，这些效应与在行为急性光效应中涉及的关键大脑部位，即副下丘脑区中的神经活动的选择性视锥对立调制有关。
总之，这些数据揭示了一种机制，即环境光照光谱的蓝移，如在曙光期间，促进了小鼠的探索行为。
