Rat neuronal nicotinic acetylcholine receptors containing α7 subunit: Pharmacological properties of ligand binding and function

Abstract

Aim: To compare pharmacological properties of heterologously expressed homomeric α7 nicotinic acetylcholine receptors (α7 nAChRs) with those of native nAChRs containing α7 subunit (α7 nAChRs) in rat hippocampus and cerebral cortex. Methods: We established a stably transfected HEK-293 cell line that expresses homomeric rat α7 nAChRs. We studies ligand binding profiles and functional properties of nAChRs expressed in this cell line and native rat α7 nAChRs in rat hippocampus and cerebral cortex. We used [ 125 I]-α-bungarotoxin to compare ligand binding profiles in these cells with those in rat hippocampus and cerebral cortex. The functional properties of the α7 nAChRs expressed in this cell line were studied using whole-cell current recording. Results: The newly established cell line, KXα7R1, expresses homomeric α7 nAChRs that bind [ 125 I]-α-bungarotoxin with a K d value of 0.380.06 nmol/L, similar to K d values of native rat α7 nAChRs from hippocampus (K d =0.280.03 nmol/L) and cerebral cortex (K d =0.330.05 nmol/L). Using whole-cell current recording, the homomeric α7 nAChRs expressed in the cells were activated by acetylcholine and ()-nicotine with EC 50 values of 28019 mol/L and 18040 mol/L, respectively. The acetylcholine activated currents were potently blocked by two selective antagonists of α7 nAChRs, α-bungarotoxin (IC 50 =192 nmol/L) and methyllycaconitine (IC 50 =10010 pmol/L). A comparative study of ligand binding profiles, using 13 nicotinic ligands, showed many similarities between the homomeric α7 nAChRs and native α7 receptors in rat brain, but it also revealed several notable differences. Conclusion: This newly established stable cell line should be very useful for studying the properties of homomeric α7 nAChRs and comparing these properties to native α7 nAChRs. © 2009 CPS and SIMM.