Differential distribution of synaptic terminals on intracellularly marked giant interneurons of the lamprey, Lampetra japonica.

Differential distribution of synaptic terminals on the soma and dendrites of lamprey (Lampetra japonica) giant interneurons were investigated with electron microscope after marking them intracellularly with Procion scarlet. Synaptic terminals were classified by the morphology of their synaptic vesicles as S (spherical) or F (flat). The ratio of F-terminals to S-terminals (F/S) on the somata was 2.62 from 5 neurons (number of terminals observed, n = 527), and that on the dendrites from 3 neurons was 0.71 (n = 348). The physiological meanings of differential distribution of synaptic terminals were discussed.