Journal of Neuroscience, Vol 1, 650-657, Copyright © 1981 by Society for Neuroscience
Light microscopic analysis of contacts between pairs of identified leech neurons with combined use of horseradish peroxidase and lucifer yellow
SA DeRiemer and ER Macagno
Intracellular injections of horseradish peroxidase (HRP) and Lucifer Yellow
(LY) were used to determine the locations of possible synaptic contacts
between pairs of identified leech neurons. The pairs studied were
ipsilateral touch sensory neurons (T cells), T cells plus the large
longitudinal motoneuron (L cell), and T cells plus the annulus erector
motoneuron (AE cell). The joint use of epi-fluorescence and transmitted
light permitted the simultaneous observation of the processes of the HRP-
and LY-filled cells. Our results indicate that, within the resolution of
the light microscope, (a) over 40% of the varicosities of a T cell are in
contact with those of another ipsilateral T cell, (b) both ipsilateral and
contralateral T cells make numerous contacts with the two motoneurons
studied, and (c) T cell- motoneuron contacts are distributed widely within
the region where the cells overlap in the neuropil and occur on both major
and minor processes of the motoneurons.