Mating-induced transient inhibition of responses to sex pheromone in a male moth is not mediated by octopamine or serotonin
Journal of Experimental Biology. 2010-03-12; 213(7): 1100-1106
DOI: 10.1242/jeb.040139
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In the male moth, Agrotis ipsilon, mating induces a transient inhibition of
behavioural and central nervous responses to sex pheromone. Newly mated males are
not attracted to sex pheromone, and the sensitivity of their antennal lobe (AL)
neurons is lower than in virgin males. This rapid transient olfactory inhibition
prevents them from re-mating unsuccessfully until they have refilled their sex
glands. We hypothesized that this olfactory ‘switch off’ might be controlled by
neuromodulators such as biogenic amines. To test our hypothesis, we studied the
effects of octopamine (OA) and serotonin (5-hydroxytryptamine, 5-HT) on the
coding properties of pheromone-sensitive AL neurons in virgin and newly mated
males. We show that AL neuron sensitivity increased in newly mated males after
injection of OA or 5-HT, but only OA treatment affected certain response
characteristics of AL neurons in virgin males. Whereas all measured AL neuron
response characteristics were different between virgin and newly mated males,
amine treatment in newly mated males restored only the latency and spike
frequency, but not the duration of excitatory and inhibitory phases, which were
initially found in virgin males. Additionally, we investigated the behavioural
effects of OA and 5-HT treatments in virgin and mated males. Although OA and 5-HT
enhanced the general flight activity of newly mated males, amine treatments did
not restore the behavioural pheromone response of mated moths. Altogether, these
results show that, although biogenic amines modulate the olfactory system in
moths, OA and 5-HT are probably not involved in the post-mating inhibition of
responses to sex pheromone in A. ipsilon males.