Fig. 2

Itch provoking scratching caused pain and pruritus will be together transmitted to the center. Pain will be conveyed to the brain via spinal nerve cells, feedback to the periphery to reduce itching. Itch through 5-HT receptor activation GRPR + neurons and spinal projection neurons aggregated to excitatory synapses transferred to the brain, and the brain feedback to the periphery to aggravate itching causing a new “itch-scratch cycle”