Agonist pharmacology of the neuronal α7 nicotinic receptor expressed in Xenopus oocytes

Abstract
The potencies and efficacies of seven agonists at chick α7 nicotinic receptors expressed in Xenopus oocytes were determined by whole cell recording. (+)-Anatoxin-a was the most potent agonist (EC50 = 0.58 μM) and acetylcholine was the least potent (EC50 = 320 μM). The rank order of agonist potencies was: (+)-anatoxin-a ⪢ cytisine > (−)-nicotine > (+)-nicotine > DMPP > 1-acetyl-4-methylpiperazine methiodide > acetylcholine. DMPP evoked only very small currents: comparison of maximally effective agonist concentrations showed that DMPP was only one-fifth as efficacious as other agonists. Previously published IC50 values for rat brain [125I]α-bungarotoxin sites show a similar agonist profile, and the identity of homo-oligomeric α7 receptors with native α-bungarotoxin-sensitive neuronal nicotinic receptors is discussed.