ABOUT 90% of neurons in dorsal root ganglia (DRGs) of rats 2-5 weeks of age
are depolarized and excited by impulse activity in neighboring neurons tha
t share the same DRG. Synaptic contacts are extremely rare in DRGs, but ins
tances of close membrane apposition between pairs of neuronal somata are no
t uncommon, especially in prenatal rats. Close membrane apposition could pe
rmit electrotonic interactions among neighboring DRG neurons. We carried ou
t an ultrastructural examination of DRGs taken from rats 2-5 weeks of age a
nd found that by this age < 2% of cells remain in close apposition with nei
ghbors. The remainder are separated by one or two layers of satellite glial
cytoplasm. It is, therefore, unlikely that close apposition between adjace
nt neurons contributes significantly to functional cross-excitation in the
DRG. (C) 1998 Lippincott Williams & Wilkins.