ULTRASTRUCTURAL IDENTIFICATION OF CATECHOLAMINE-CONTAINING CENTRAL SYNAPTIC TERMINALS

Abstract

Cytochemical methods for the localization of central catecholamine-containing synaptic terminals have been developed from an extensive foundation of biochemical work and from extrapolation of results on the peripheral sympathetic nervous system. Direct localization of catecholamines in central nerve terminals in some parts of the brain can now be obtained by fixation with permanganates. More broadly applicable, but less direct localizing methods depend upon selective accumulation of tritiated catecholamines for autoradiography or the accumulation of reactive catecholamine congeners which act as markers with conventional fixation. The pattern of acute degenerative changes which result after treatment with 6-hydroxydopamine can also be used to provide an indirect localization of the terminals which had stored catecholamines. When the results of each of the methods are combined, the present techniques indicate that catecholamine-containing terminals in the brain can be identified more confidently than any other system of neurotransmitter substances. Nevertheless, there is considerable need for future cytochemical innovation.