<prompt> Counter irritants applied to decrease pain by action onSpatial summationInhibition of pain pathways in the dorsal horn gatePain receptor saturationDorsal root ganglia  <response>: B Inhibition of pain pathways in the dorsal horn gate Central Inhibition Counterirritants Stimulation with an electric vibrator at the site of pain also gives some relief. The relief is due primarily to inhibition of pain path- ways in the dorsal horn gate by stimulation of large-diameter touch-pressure afferents. The same mechanism is probably responsible for the efficacy of counterirritants. Stimulation of the skin over an area of visceral inflammation produces some relief of the pain due to the visceral disease. The old-fashioned mustard plaster works on this principle. 