Journal of Neuroscience, Vol 8, 353-367, Copyright © 1988 by Society for Neuroscience
Radiation-induced reduction of the glial population during development disrupts the formation of olfactory glomeruli in an insect
LA Oland, LP Tolbert and KL Mossman
Department of Anatomy and Cell Biology, Georgetown University School of Medicine, Washington, D.C. 20007.
Interactions between neurons and between neurons and glial cells have been
shown by a number of investigators to be critical for normal development of
the nervous system. In the olfactory system of Manduca sexta, sensory axons
have been shown to induce the formation of synaptic glomeruli in the
antennal lobe of the brain (Hildebrand et al., 1979). Oland and Tolbert
(1987) found that the growth of sensory axons into the developing antennal
lobe causes changes in glial shape and disposition that presage the
establishment of glomeruli, each surrounded by a glial envelope. Several
lines of evidence lead us to hypothesize that the glial cells of the lobe
may be acting as intermediaries in developmental interactions between
sensory axons and neurons of the antennal lobe. In the present study, we
have tested this hypothesis by using gamma-radiation to reduce the number
of glial cells at a time when neurons of the antennal system are
postmitotic but glomeruli have not yet developed. When glial numbers are
severely reduced, the neuropil of the resulting lobe lacks glomeruli.
Despite the presence of afferent axons, the irradiated lobe has many of the
features of a lobe that developed in the absence of afferent axons. Our
findings indicate that the glial cells must play a necessary role in the
inductive influence of the afferent axons.