Optogenetic surface stimulation of the rat cervical spinal cord

Area of Science:

• Neuroscience
• Regenerative Medicine
• Biotechnology

Background:

• Electrical intraspinal microstimulation (ISMS) activates spinal cord circuits for motor control and recovery after injury.
• ISMS lacks cell-type specificity and is invasive, necessitating alternative approaches.
• Optogenetics offers a less invasive, cell-specific method for neural circuit modulation.

Purpose of the Study:

• To investigate optogenetic spinal stimulation (OSS) as an alternative to ISMS for forelimb muscle activation in rats.
• To map forelimb muscle activation and movement evoked by OSS at various cervical spinal cord sites.
• To explore the influence of adeno-associated virus (AAV) injection parameters on OSS efficacy.

Main Methods:

• Adeno-associated viruses (AAV) encoding channelrhodopsin-2 (ChR2) or Chronos were injected into the rat cervical spinal cord.
• Optogenetic stimulation was applied to 16 sites along the dorsal spinal cord surface after viral incubation.
• Forelimb muscle activation and movement patterns were assessed in response to OSS.

Main Results:

• OSS successfully evoked distinct forelimb muscle activation and complex movements.
• The volume and depth of AAV injections were found to be critical for modulating OSS-evoked responses.
• Three distinct types of movements were observed following OSS.

Conclusions:

• Optogenetic spinal stimulation is a viable and promising method for dissecting spinal circuitry function.
• OSS provides a cell-type-specific and potentially less invasive approach compared to ISMS.
• This technique holds potential for developing targeted therapies for spinal cord injury and other neurological conditions.