Incorporation of acetylcholinesterase into synaptic vesicles is associated with blockade of synaptic transmission

THE transmission of nerve signals across cholinergic synapses involves the presynaptic release (or secretion) of acetylcholine (ACh) which, by acting on specific sites of the postsynaptic membrane, induces changes in the postsynaptic transmembrane potential. According to the vesicle hypothesis 1 , ACh is packed inside synaptic vesicles which release their contents from the nerve terminal on contact with the presynaptic membrane. Although there is abundant experimental evidence supporting the hypothesis 2 , some papers question its validity 3–6 . The most important alternative hypothesis postulates that the releasable ACh is free in the cytoplasm 3–6 and that the vesicles are a secondary reservoir containing ‘bound’ ACh.