Identification of spinal circuits transmitting and gating mechanical pain

Area of Science:

• Neuroscience
• Pain research
• Spinal cord circuitry

Background:

• Spinal cord pain processing involves nociceptive (T) neurons receiving input from nociceptors and Aβ mechanoreceptors.
• Aβ mechanoreceptor input is thought to be gated by spinal inhibitory neurons (INs).

Purpose of the Study:

• To identify critical neuronal components involved in pain transduction in the spinal cord.
• To elucidate the roles of specific excitatory and inhibitory neuron populations in mechanical pain processing.

Main Methods:

• Utilized intersectional genetic manipulations to mark and ablate six distinct populations of spinal neurons.
• Performed behavioral analyses and electrophysiological recordings to assess pain responses.

Main Results:

• Identified somatostatin-expressing (SOM+) excitatory neurons as crucial for mechanical pain transmission (T-type cells).
• Demonstrated that dynorphin-expressing (Dyn+) inhibitory neurons (INs) are essential for gating Aβ fiber input to SOM+ neurons, thereby regulating pain.
• Ablation of SOM+ neurons resulted in a loss of mechanical pain sensation.

Conclusions:

• A microcircuit comprising peripheral mechanical nociceptors, Aβ mechanoreceptors, spinal SOM+ excitatory neurons, and Dyn+ inhibitory neurons forms the basis of mechanical pain transmission and gating.
• This circuit provides a detailed framework for understanding the neurobiological mechanisms underlying mechanical pain perception.