Transport of choline by membrane vesicles prepared from synaptosomes of insect nervous tissue.

Membrane vesicles derived from synaptic plasma membranes have been isolated from insect nervous tissue. High affinity uptake of choline into these vesicles has been demonstrated using artificially imposed electrochemical gradients as the sole energy source. The transport of choline is strictly dependent on the presence of Na(+) and Cl(?) in the external medium and is mainly driven by a Na(+) gradient. Inhibition by proton ionophores and stimulation by valinomycin suggest that choline uptake is an electrogenic process which is optimal in the presence of a membrane potential. In addition, the process is inhibited by alkaloid neurotoxins veratridine and aconitine; this inhibitory effect is prevented by tetrodotoxin. The data are consistent with the predominant role of ion chemical gradients and an electrical membrane potential in energizing the uptake of choline.