Review: The nicotinic modulation of pain.

Pain is a physiological unpleasant sensation that associated with actual or potential tissue damage and affects the major part of human population. Numerous modulatory system control pain through a complex process. The drugs that regulate the modulators involving in this process are currently available; however, the studies to understand the process and develop new agents are still going on. In this review, it is aimed to relay information about how nicotinic receptors contribute the pain modulation. It is obvious that a wide variety of nicotinic receptors is located in both peripheral and central areas. Among these receptors α7, α4β2 and α9α10 receptor subtypes draw attention in terms of pain modulation. The fact that different receptor subtypes involve in different processes of different pain conditions leads to provide beneficial results from the agonism of α7, α4β2 and antagonism of α9α10. The major restraint of the usage of nAChR agonists is their adverse effects. However, nowadays, the side effects are reduced by the clinical developments. Additionally, positive allosteric modulators that amplify the effectiveness of nAChR ligands are in demand.