The metabolism of acetylcholine in the intact central nervous system of an insect (Periplaneta Americana L.)

Abstract

1. A very rapid metabolism of ³H-labelled acetylcholine has been demonstrated in the intact abdominal nerve cord. It has been shown that the cholinesterase system is effective in drastically reducing the concentration of acetylcholine in the extracellular fluid of the terminal abdominal ganglion with bathing solutions of up to IO^-2M acetylcholine. 2. Evidence has been obtained which indicates that an appreciable hydrolysis of acetylcholine occurs at the periphery of the nerve cord. This effect is correlated with the electronmicroscopic demonstration of regions of eserine-sensitive cholinesterase located on glial membranes in the periphery of ganglia and connectives. It is suggested that some hydrolysis of extraneous acetylcholine may occur in the fibrous layer of the nerve sheath as a result of an accumulation of diffusible acetylcholinesterase in this region. 3. The results are discussed in relation to the possible involvement of the conventional cholinergic system in synaptic transmission in the central nervous system of this insect.