Quantitative analysis of sex-pheromone coding in the antennal lobe of the moth Agrotis ipsilon: a tool to study network plasticity

D. Jarriault, C. Gadenne, J.-P. Rospars, S. Anton
Journal of Experimental Biology. 2009-03-27; 212(8): 1191-1201
DOI: 10.1242/jeb.024166

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To find a mating partner, moths rely on pheromone communication. Released in very
low amounts, female sex pheromones are used by males to identify and localize
females. Depending on the physiological state (i.e. age, reproductive state), the
olfactory system of the males of the noctuid moth Agrotis ipsilon is ‘switched on
or off’. To understand the neural basis of this behavioural plasticity, we
performed a detailed characterization of the qualitative, quantitative and
temporal aspects of pheromone coding in the primary centre of integration of
pheromonal information, the macroglomerular complex (MGC) of the antennal lobe.
MGC neurons were intracellularly recorded and stained in sexually mature virgin
males. When stimulating antennae of males with the three main components of the
female pheromone blend, most of the neurons showed a biphasic
excitatory-inhibitory response. Although they showed different preferences, 80%
of the neurons responded at least to the main pheromone component (Z-7-dodecenyl
acetate). Six stained neurons responding to this component had their dendrites in
the largest MGC glomerulus. Changes in the stimulus intensity and duration
affected the excitatory phase but not the inhibitory phase properties. The
stimulus intensity was shown to be encoded in the firing frequency, the number of
spikes and the latency of the excitatory phase, whereas the stimulus duration
only changed its duration. We conclude that the inhibitory input provided by
local interneurons following the excitatory phase might not contribute directly
to the encoding of stimulus characteristics. The data presented will serve as a
basis for comparison with those of immature and mated males.


Auteurs Bordeaux Neurocampus