TACR1 and diabetic neuropathy: Here, a hypothesis for the effects of exogenous EM2 on SP signaling within the SDH in painful diabetic neuropathy was proposed: compared to the normal condition, SP-NK1R signaling within lamina I was not sensitized in the case of DNP during nociceptive message transmission; In addition, SP-NK1R signaling activated by noxious stimuli was insusceptible to exogenous EM2, probably owing to the loss of presynaptic MORs in the condition of diabetic neuropathy.