London: Karolinska Institutet researchers have created a genetically modified mouse in which certain neurons can be activated by blue light, a development that is of potential significance to the recovery of walking after spinal cord injury. Shining blue light on brainstems or spinal cords isolated from these mice produces walking-like motor activity, the study published in the scientific journal Nature Neuroscience stated.
By inserting ChR2 into nerve cells expressing Vglut2 - a transporter found in most excitatory neurons in the brainstem and spinal cord as well as many excitatory neurons in other regions of the brain - they created a Vglut2-ChR2 mouse . The reason for doing this was to be able to selectively activate excitatory neurons in specific regions of the brainstem and spinal cord, as the excitatory neurons are believed to be important for initiating locomotion, or walking.The researchers then recorded from motor nerves leaving the spinal cord. When blue light was shined directly on the spinal cord, walking-like activity began and was maintained for the duration of the light pulse. This proved that activation of Vglut2-expressing excitatory neurons in the spinal cord is sufficient for walking. Walking-like activity could also be initiated by exposing the lower brainstem to blue light, demonstrating that excitatory cells in the brainstem provide a sufficient ``go`` signal to the spinal neurons involved in walking. ANI
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