Electroacupuncture relieves stress-induced pain through thalamic nerve cells for limb pain, while abdominal and spontaneous pain likely involve separate pathways.
Male mice underwent repeated restraint stress to induce pain hypersensitivity. Researchers measured sensitivity to mechanical and heat stimuli in the paws and abdomen, as well as spontaneous pain-like behaviours. They used chemical genetic methods to selectively suppress or activate calcium/calmodulin-dependent protein kinase two alpha-positive neurons in the ventral anterior-lateral thalamic complex, and applied electroacupuncture at Zusanli and Sanyinjiao acupuncture points.
Chronic stress produced widespread mechanical and heat hypersensitivity and increased spontaneous pain-like behaviours. Suppressing the targeted thalamic neurons reduced these effects, whereas activating them in unstressed mice reproduced them, identifying these cells as key drivers of stress-related pain. Electroacupuncture improved all measured pain behaviours, but its benefits for paw mechanical and heat sensitivity depended on suppressing the targeted thalamic neurons, while its effects on abdominal sensitivity and spontaneous pain appeared to operate through other mechanisms.
