Methamphetamine and 3,4-methylenedioxymethamphetamine interact with central nicotinic receptors and induce their up-regulation

Abstract

Previous work from our group indicated that α7 nicotinic acetylcholine receptors (α7 nAChR) potentially play a role in methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA) neurotoxicity. The aims of the present study were two-fold: (1) to demonstrate the interaction of METH and MDMA with homomeric α7 nAChR ([ 3H]methyllycaconitine binding) and other heteromeric subtypes ([ 3H]epibatidine binding); and (2) to show the effects of amphetamine derivative pretreatment on the density of binding sites. METH and MDMA displaced [ 3H]methyllycaconitine and [ 3H]epibatidine binding in membranes from NGF-differentiated PC 12 cells and mouse brain, with K i values in the micromolar range, MDMA revealing a greater affinity than METH. In addition, METH and MDMA induced a time- and concentration-dependent increase in [ 3H]methyllycaconitine and [ 3H]epibatidine binding; which had already been apparent after 6 h of pretreatment, and which peaked in differentiated PC 12 cells after 48 h. The highest increases were found in [ 3H]epibatidine binding, with MDMA inducing higher increases than METH. Treatment with METH and MDMA increased B max of high-affinity sites for both radioligands without affecting K d. The heightened binding was inhibited by pretreatment with cycloheximide, suggesting the participation of newly synthesised proteins while inhibition of protein trafficking to plasma membrane did not block up-regulation. The effects of protein kinase and cyclophilin inhibitors on such up-regulation were explored, revealing a rapid, differential and complex regulation, similar to that described for nicotinic ligands. All of these results demonstrate that METH and MDMA have affinity for, and can interact with, nAChR, inducing their up-regulation, specially when higher doses are used. Such effects may have a role in METH- and MDMA-induced neurotoxicity, cholinergic neurotransmission, and in processes related to addiction and dependence.