CHRNA4 and neuropathic pain: However, we choose to perform behavior experiments on different species of animals is because this study was designed to test whether the selective agonist of α4β2 subtype of nAChR (TC-2559) has antinociceptive effects and its possible mechanism, thus to test whether the agonist of α4β2 subtype of nAChR is capable to be developed as new common analgesic drug for treatment of neuropathic pain.