Mating-induced differential sex pheromone and plant odour processing in a male moth.

3. BARROZO RB, GADENNE C, ANTON S.

GOETTINGEN

Simposio; 9th Goettingen Meeting of the German Neuroscience Society; 2011

Innate behaviours in animals can be modulated by factors such as the environment, experience or the physiological state. This behavioural plasticity originates from changes in the underlying neuronal substrate. A well-described form of plasticity is induced by mating. In both vertebrates and invertebrates, males experience a post-ejaculatory refractory period during which they avoid new females. In the male moth Agrotis ipsilon, mating induces a transient inhibition of responses to the female-produced sex pheromone. To understand the neural bases of this inhibition and its possible odour specificity, we carried out a detailed analysis of the peripheral and central olfactory system and the behaviour of male A. ipsilon, using sex pheromone, plant volatiles, and their mixture. We found that although mating changes the coding properties of central pheromone-sensitive neurons in the antennal lobe (the macroglomerular complex, MGC), thus affecting the post-mating behaviour, the sensory input remains constant. Besides, the post-mating inhibition does not affect the processing of a behaviourally attractive flower volatile, heptanal in the ordinary glomeruli (OG). When challenged with mixtures of sex pheromone and the flower volatile, additional evidence for differential processing of odours was found. Whereas synergism was observed in virgin males, the sex pheromone leads to inhibitory effects in mated males in the OGs, in correlation with behavioural changes. We propose the existence of a complex inhibitory system in which responses of males to the female sex-pheromone depend on their mating status but also on the presence of other biologically relevant odours (heptanal). We provide evidence for a transient odour-selective central mechanism leading to post-mating sexual inhibition in males, which is interpreted as a "refusal to respond", but not as exhaustion behaviour as described in vertebrates.