Glutamatergic and GABAergic neurons in the vLGN mediate the nociceptive effects of green and red light on neuropathic pain

Phototherapy is an emerging non-pharmacological treatment for depression, circadian rhythm disruptions, and neurodegeneration, as well as pain conditions including migraine and fibromyalgia. However, the mechanism of phototherapy-induced antinociception is not well understood. Here, using fiber photometry recordings of population-level neural activity combined with chemogenetics, we found that phototherapy elicits antinociception via regulation of the ventral lateral geniculate body (vLGN) located in the visual system. Specifically, both green and red lights caused an increase of c-fos in vLGN, with red light increased more. In vLGN, green light causes a large increase in glutamatergic neurons, whereas red light causes a large increase in GABAergic neurons. Green light preconditioning increases the sensitivity of glutamatergic neurons to noxious stimuli in vLGN of PSL mice. Green light produces antinociception by activating glutamatergic neurons in vLGN, and red light promotes nociception by activating GABAergic neurons in vLGN. Together, these results demonstrate that different colors of light exert different pain modulation effects by regulating glutamatergic and GABAergic subpopulations in the vLGN. This may provide potential new therapeutic strategies and new therapeutic targets for the precise clinical treatment of neuropathic pain.

Automated summary

Phototherapy is a emerging non-pharmacological treatment that can be used for depression, circadian rhythm disruptions, neurodegeneration, and pain conditions. The mechanism of phototherapy-induced antinociception is not well understood. This study found that phototherapy regulates the ventral lateral geniculate body (vLGN) in the visual system to elicit antinociception. Specifically, green light activates glutamatergic neurons and produces antinociception, while red light activates GABAergic neurons and promotes nociception in the vLGN. These findings suggest that different colors of light can modulate pain through different neural subpopulations in the vLGN, providing potential therapeutic strategies for neuropathic pain.