Rat neuronal nicotinic acetylcholine receptors containing alpha7 subunit: pharmacological properties of ligand binding and function.
OBJECTIVE
To compare pharmacological properties of heterologously expressed homomeric alpha7 nicotinic acetylcholine receptors (alpha7 nAChRs) with those of native nAChRs containing alpha7 subunit (alpha7* nAChRs) in rat hippocampus and cerebral cortex.


METHODS
We established a stably transfected HEK-293 cell line that expresses homomeric rat alpha7 nAChRs. We studies ligand binding profiles and functional properties of nAChRs expressed in this cell line and native rat alpha7* nAChRs in rat hippocampus and cerebral cortex. We used [(125)I]-alpha-bungarotoxin to compare ligand binding profiles in these cells with those in rat hippocampus and cerebral cortex. The functional properties of the alpha7 nAChRs expressed in this cell line were studied using whole-cell current recording.


RESULTS
The newly established cell line, KXalpha7R1, expresses homomeric alpha7 nAChRs that bind [(125)I]-alpha-bungarotoxin with a K(d) value of 0.38+/-0.06 nmol/L, similar to K(d) values of native rat alpha7* nAChRs from hippocampus (K(d)=0.28+/-0.03 nmol/L) and cerebral cortex (K(d)=0.33+/-0.05 nmol/L). Using whole-cell current recording, the homomeric alpha7 nAChRs expressed in the cells were activated by acetylcholine and (-)-nicotine with EC(50) values of 280+/-19 micromol/L and 180+/-40 micromol/L, respectively. The acetylcholine activated currents were potently blocked by two selective antagonists of alpha7 nAChRs, alpha-bungarotoxin (IC(50)=19+/-2 nmol/L) and methyllycaconitine (IC(50)=100+/-10 pmol/L). A comparative study of ligand binding profiles, using 13 nicotinic ligands, showed many similarities between the homomeric alpha7 nAChRs and native alpha7* receptors in rat brain, but it also revealed several notable differences.


CONCLUSIONS
This newly established stable cell line should be very useful for studying the properties of homomeric alpha7 nAChRs and comparing these properties to native alpha7* nAChRs.
Xiao
Yingxian
Y
Department of Pharmacology, Georgetown University School of Medicine, Washington, DC 20057, USA.
Abdrakhmanova
Galya R
GR
Baydyuk
Maryna
M
Hernandez
Susan
S
Kellar
Kenneth J
KJ
D000109:Acetylcholine / Q000494:pharmacology*; D000157:Aconitine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002540:Cerebral Cortex / Q000378:metabolism; D015870:Gene Expression; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008024:Ligands; D009474:Neurons / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D064569:alpha7 Nicotinic Acetylcholine Receptor
C579167:Chrna7 protein, human; C579165:Chrna7 protein, rat; D008024:Ligands; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; C054634:methyllycaconitine; D009538:Nicotine; D000109:Acetylcholine; D000157:Aconitine