Studies on a possible functional coupling between presynaptic acetylcholinesterase and high-affinity choline uptake in the rat brain.
The relationships between presynaptic acetylcholinesterase (AChE) and high-affinity choline uptake (HACU) were investigated using a monolayer of rat cortex synaptosomes in superfusion conditions. The following sets of experiments were performed: determination of [3H]choline ([3H]Ch) uptake during superfusion with [3H]Ch; determination of [3H]Ch uptake during superfusion with acetylcholine (ACh) tritiated in the Ch moiety; evaluation of ACh hydrolysis during superfusion with ACh labelled in the acetate moiety; and comparison of the uptake of [3H]Ch generated by hydrolysis of [3H]ACh with that occurring during superfusion with [3H]Ch. Intact ACh was not taken up by superfused synaptosomes. The uptake of [3H]Ch during superfusion with 1 or 0.1 microM [N-methyl-3H]ACh was two-thirds of that occurring during superfusion with the same concentrations of [3H]Ch. The amount of [3H]Ch produced by hydrolysis during 16 min of superfusion was 1/25 of the amount passing through the synaptosomal monolayer during 16 min of superfusion with [3H]Ch. The results indicate that presynaptic AChE and HACU are located in close proximity to each other on the cholinergic terminal membrane, an observation suggesting the possibility of a functional coupling between the two mechanisms.
D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000201:enzymology*; D013574:Synaptosomes / Q000201:enzymology
D000110:Acetylcholinesterase; D002794:Choline