α4β2 subunit combination specific pharmacology of neuronal nicotinic acetylcholine receptors in N1E-115 neuroblastoma cells

Abstract

Pharmacological characteristics of native neuronal nicotinic acetylcholine receptor-mediated ion currents in mouse N1E-115 neuroblastoma cells have been investigated by superfusion of voltage clamped cells with known concentrations of the agonists acetylcholine, nicotine and cytisine, and the antagonists α-bungarotoxin and neuronal bungarotoxin. The sensitivity of the nicotinic acetylcholine receptor for agonists followed the agonist potency rank-order: nicotine ≈ acetylcholine ≫ cytisine. The EC 50 values of acetylcholine and nicotine are 78 μM and 76 μM, respectively. Equal concentrations of acetylcholine and nicotine induce inward currents with approximately the same peak amplitude, whereas cytisine induces much smaller inward currents. Acetylcholine-induced currents are unaffected by high concentrations of α-bungarotoxin. Conversely, at 10 and 90 nM neuronal bungarotoxin reduces the amplitude of the 1 mM acetylcholine-induced inward current to 47% and 11% of control values, respectively. Both the agonist potency rank-order and the differential sensitivity to snake toxins of nicotinic receptors in N1E-115 cells are consistent with the known pharmacological profile of α4β2 nicotinic receptors expressed in Xenopus oocytes and distinct from those of all other nicoonic acetylcholine receptors of known functional subunit compositions. All data indicate that the native nicotinic acetylcholine receptor in N1E-115 cells is an assembly of α4 and β2 subunits, the putative major subtype of nicotinic acetylcholine receptor in the brain.