Rat a3/b4 subtype of neuronal nicotinic acetylcholine receptor stably expressed in a transfected cell line: pharmacology of ligand binding and function

We stably transfected human kidney embryonic 293 cells with the rat neuronal nicotinic acetylcholine receptor (nAChR) a3 and b4 subunit genes. This new cell line, KXa3b4R2, expresses a high level of the a3/b4 receptor subtype, which binds (6)- [3H]epibati-dine with a Kd value of 304616 pM and a Bmax value of 8942 6 115 fmol/mg protein. Comparison of nicotinic drugs in competing for a3/b4 receptor binding sites in this cell line and the binding sites in rat forebrain (predominantly a4/b2 receptors) revealed marked differences in their Ki values, but similar rank orders of potency for agonists were observed, with the exception of anatoxin-A. The affinity of the competitive antagonist dihydro-b-erythroidine is.7000 times higher at a4/b2 receptors in rat forebrain than at the a3/b4 receptors in these cells. The a3/b4 nAChRs expressed in this cell line are functional, and in response to nicotinic agonists, 86Rb1 efflux was increased to levels 8–10 times the basal levels