Radioautographic study of 5-hydroxytryptamine-containing nerve terminals in central ganglia ofPlanorbis corneus: comparison with other species and characteristics of the serotoninergic nerve terminal

Central ganglia fromPlanorbis corneus were incubated with [3H] 5-hydroxytryptamine and [3H]-leucine. After fixation, sections were examined by light and electron microscopic autoradiography. With [3H] 5-hydroxytryptamine there was a high level of uptake into a small number of axons and terminal processes in the neuropil. The terminal processes contained granular vesicles (diameter 50–120 nm), some of which possessed eccentrically placed cores, and agranular vesicles (mean diameter 60 nm). No membrane synaptic specializations were observed. With [3H] leucine there was a general distribution of radioactivity throughout the ganglia.