Interaction of choline with nicotinic and muscarinic cholinergic receptors in the rat brain in vitro

The ability of choline to interact with nicotinic receptors was investigated by measuring its ability to inhibit the specific binding of [3H]-nicotine in rat brain. Choline, with an IC50 of 241 mumol/l, was three times more potent than its analogue deanol and almost 1000-fold less potent than acetylcholine. Choline also inhibited the binding of the antagonist [3H]-quinuclidinyl benzilate (IC50 = 2.5 mmol/l) and of the agonist [3H]-oxotremorine-M (IC50 = 165 mumol/l) to muscarinic cholinergic receptors. These results indicate that choline is able to interact directly, in vitro with brain cholinergic receptors of both the nicotinic and muscarinic type.