PT  - JOURNAL ARTICLE
AU  - C J Hillard
AU  - J J Pounds
TI  - [3H]tetraphenylphosphonium accumulation in cerebral cortical synaptosomes as a measure of nicotine-induced changes in membrane potential.
DP  - 1991 Dec 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1118--1123
VI  - 259
IP  - 3
4099  - http://jpet.aspetjournals.org/content/259/3/1118.short
4100  - http://jpet.aspetjournals.org/content/259/3/1118.full
SO  - J Pharmacol Exp Ther1991 Dec 01; 259
AB  - The effect of nicotine on synaptosomal membrane potential in P2 preparations of rat cerebral cortex was investigated using a membrane permeant, lipophilic cation, [3H]tetraphenylphosphonium ([3H]TPP+). [3H]TPP+ accumulated in synaptosomes in a time-dependent manner and its accumulation was decreased when the extracellular potassium concentration was increased and in the presence of the sodium channel toxin, veratridine. Nicotine (1-1000 microM) decreased the accumulation of [3H]TPP+ in both P2 synaptosomal preparations and in synaptosomes purified using Percoll gradients. This effect of nicotine was mimicked by other nicotinic agonists (1,1-dimethyl-4-phenylpiperazinium iodide, cytisine, suberyldicholine and acetylcholine) and was partially blocked by 10 microM mecamylamine and 30 microM hexamethonium. Atropine (1 microM) and the removal of calcium from the incubation mixture both enhanced the effect of nicotine while the addition of physostigmine (10 microM) reduced the nicotine-induced decrease in [3H]TPP+ accumulation, evidence that acetylcholine released from the synaptosomes by nicotine may produce hyperpolarization of synaptosomes via stimulation of presynaptic muscarinic receptors. It is concluded that the effect of nicotine on [3H]TPP+ accumulation is mediated by nicotine stimulation of a ganglionic-type nicotinic cholinergic receptor and that this method of determining synaptosomal membrane potential will provide a functional measure of presynaptic nicotinic receptor activation.