JN403, in vitro characterization of a novel nicotinic acetylcholine receptor α7 selective agonist

Abstract

This report describes the in vitro features of a novel selective nicotinic acetylcholine receptor (nAChR) α7 agonist, JN403, (S)-(1-Aza-bicyclo[2.2.2]oct-3-yl)-carbamic acid (S)-1-(2-fluoro-phenyl)-ethyl ester. JN403 was evaluated in a number of in vitro systems of different species, at recombinant receptors using radioligand binding, signal transduction and electrophysiological studies. When using [ 125I] α-bungarotoxin (α-BTX) as a radioligand, JN403 has high affinity for human recombinant nAChR α7 (p K D = 6.7). Functionally, JN403 is a partial and potent agonist at human nAChR α7. The compound stimulates calcium influx in GH3 cells recombinantly expressing the human nAChR with an pEC 50 of 7.0 and an E max of 85% (compared to the full agonist epibatidine). In Xenopus oocytes expressing human nAChR α7 JN403 induces inward currents with an pEC 50 of 5.7 and an E max of 55%. In both recombinant systems JN403 is a partial agonist and the agonistic effects are blocked after pre-administration of methyllycaconitine (MLA, 100 nM), a nAChR α7 antagonist. In functional calcium influx assays, JN403 displays a significantly lower potency for other subtypes of human nAChRs like α4β2, α3β4, α1β1γδ as well as 5HT 3 receptors when tested functionally as an antagonist (pIC 50 < 4.8) and is devoid of agonistic activity (pEC 50 < 4). Similarly, JN403 shows low binding activity at a wide panel of neurotransmitter receptors. Thus, JN403 is a potent and selective nAChR α7 agonist and will be a useful tool for the characterization of nAChR α7 mediated effects both in vitro and in vivo.