Journal of Neuroscience, Vol 3, 987-994, Copyright © 1983 by Society for Neuroscience
High affinity choline uptake and calcium-dependent acetylcholine release in proteoliposomes derived from rat cortical synaptosomes
EM Meyer and JR Cooper
Proteoliposomes were prepared from rat cortical synaptic plasma membranes
that retained high and low affinity choline transport. High affinity
transport was inhibited by hemicholinium-3 in a competitive manner and was
apparently dependent on membrane potential or ion gradients.
Proteoliposomes supplemented with an acetylcholine- generating system were
able to synthesize [3H]ACh de novo from [3H]choline taken up by high or low
affinity transport; however, we were able to specifically load
proteoliposomes derived from cholinergic membranes by using a low choline
concentration. [3H]ACh, but not [3H]choline, was subsequently released in a
calcium-dependent manner by K+ depolarization. This preparation offers a
simplified membrane system for studying functional high affinity choline
transport and nonvesicular ACh release.