The Journal of Neuroscience, August 15, 2001, 21(16):6274-6282
Odor Exposure Causes Central Adaptation and Morphological Changes
in Selected Olfactory Glomeruli in Drosophila
Jean-Marc
Devaud,
Angel
Acebes, and
Alberto
Ferrús
Instituto Cajal, Consejo Superior de Investigaciones
Científicas, Madrid E-28002, Spain
In an attempt to correlate behavioral and neuronal changes, we
examined the structural and functional effects of odor exposure in
Drosophila. Young adult flies were exposed to a high
concentration of the selected odor, usually benzaldehyde or isoamyl
acetate, for 4 d and subsequently tested for their olfactory
response to a variety of odorants and concentrations. The behavioral
response showed specific adaptation to the exposed odor. By contrast,
olfactory transduction, as measured in electroantennograms, remained
normal. In vivo volume measurements were performed on
olfactory glomeruli, the anatomical and functional units involved in
odor processing. Pre-exposed flies exhibited volume reduction of
certain glomeruli, in an odor-selective manner. Of a sample of eight
glomeruli measured, dorsal medial (DM) 2 and ventral (V)
were affected by benzaldehyde exposure, whereas DM6 was affected
by isoamyl acetate. Estimation of the number of synapses
indicates that volume reduction involves synapse loss that can reach
30% in the V glomerulus of flies adapted to benzaldehyde. Additional
features of odorant-induced adaptation, including concentration
dependence and perdurance, also show correlation, because both effects
are elicited by high odor concentrations and are long-lasting (>1
week). Finally, the dunce mutant fails to develop
behavioral adaptation as well as morphological changes in the olfactory
glomeruli after exposure. These neural changes thus appear to require
the cAMP signaling pathway.
Key words:
adaptation; olfactory glomeruli; memory; synapse number; dunce; Drosophila
Copyright © 2001 Society for Neuroscience 0270-6474/01/21166274-09$05.00/0
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