Stable expression in HEK-293 cells of the rat alpha 3/ beta 4 subtype of neuronal nicotinic acetylcholine receptor

The alpha 3/ beta 4 subtype of neuronal nicotinic acetylcholine receptor (nAChR) was stably expressed in human embryonic kidney (HEK) 293 cells that co-expressed-a voltage-gated Ca super(2+) channel. alpha 3 / beta 4-nAChR-expressing clones were identified using the fura-2 Ca super(2+) imaging technique, and were further characterised by single-cell and whole-cell patch-clamp studies. Acetylcholine (ACh) induced fast activating currents which showed desensitisation and inward rectification. The conductance of the ACh-activated channel was 29 pS. The order of potency of the nicotinic agonists tested was cytisine approximately equal to nicotine>acetylcholine. The EC sub(50) value for ACh was 145 mu M; the Hill coefficient was close to 2. The currents elicited by ACh were effectively blocked by nicotinic antagonists, but not by the muscarinic antagonist atropine. These properties are comparable to the pharmacological and physiological profile of ganglionic nicotinic receptors and type III currents of cultured hippocampal neurons.