Allosteric modulation of α4β2* nicotinic acetylcholine receptors: Desformylflustrabromine potentiates antiallodynic response of nicotine in a mouse model of neuropathic pain

Abstract

BackgroundNeuronal nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels. The 42 subtype of nAChRs plays an important role in the mediation of pain and several nicotine-evoked responses. Agonists and partial agonists of 42 nAChRs show efficacy in animal pain models. In addition, the antinociceptive properties of nicotine, a non-selective nAChR agonist with a high affinity for 42 nAChRs, is well-known. There is a growing body of evidence pointing to allosteric modulation of nAChRs as an alternative treatment strategy in experimental pain. Desformylflustrabromine (dFBr) is a positive allosteric modulator (PAM) at 42 nAChRs that enhances agonist responses without activating receptors. We hypothesized that dFBr may enhance nicotine-induced antinociception. MethodsThe present study investigated whether dFBr could attenuate mouse chronic constriction injury (CCI)-induced neuropathic pain by increasing endogenous cholinergic tone or potentiating the nicotine-evoked antiallodynic response. ResultsWe found that subcutaneous administration of dFBr failed to reduce pain behaviour on its own. However, the combination of dFBr with nicotine significantly reversed neuropathic pain behaviour dose- and time-dependently without motor impairment. Our data revealed that this effect was mediated by the 42 nAChRs by using competitive 42 antagonist dihydro--erythroidine. In addition, dFBr failed to potentiate the antiallodynic effect of morphine, which shows the effect of dFBr is unique to 42 nAChRs. ConclusionsThe present results suggest that allosteric modulation of 42 nAChR may provide new strategies in chronic neuropathic pain. Significance42 nAChRs are involved in pain modulation. dFBr, a PAM at 42 nAChRs, potentiates the nicotine response dose-dependently in neuropathic pain. Thus, the present results suggest that allosteric modulation of 42* nAChR may provide new strategies in chronic neuropathic pain.