Olfactory plasticity in insect: the role of biogenic amines on pheromone sensitivity.

BARROZO RB, SIMEONE X, GADENNE C, ANTON S.

Roscoff, Francia

Congreso; 10th European Symposion of Taste and Olfaction; 2007

Odour perception in insects is directly influenced by diverse internal and external factors such as the reproductive status, age, experience, and photoperiod. An identical stimulus may elicit distinct reactions under different environmental or behavioural conditions. Since neural circuits are in finite number in animals, neurons and networks must accomplish multiple functions. Therefore, neuromodulation provides a potent means to reach functional and reversible adjustments of a sensory circuit. The olfactory system is an attractive model for the study of neuronal wiring and information processing. In moths, the sensitivity to the sex pheromone may vary with the physiological state of the insects as well as with experience. Such phenomena have been shown at the behavioural and at the central nervous level. In males of Agrotis ipsilon, the behavioural and central nervous responses to sex pheromone increase with age and juvenile hormone levels (Anton and Gadenne, 1999). On the other hand, a transient post-mating inhibition of behavioural and central nervous responses to sex pheromone was also observed (Gadenne et al 2001). This transient neuronal plasticity serves as an energy-saving strategy by switching off the olfactory system and therefore preventing males from mating unsuccessfully. Thus, nocturnal moths are able to progressively set in motion or disengage their olfactory system in correlation with their physiological state. Neuromodulators like the biogenic amines octopamine (OA) and serotonin (5HT) could be implicated in this task. Both have been shown to be involved in regulating sex-specific behaviour, and to modulate peripheral and central nervous processing of pheromones in insects and 5HT even in vertebrates. We combined behavioural studies, intracellular recording techniques and biochemical methods to investigate the role of OA and 5HT in the plasticity of the olfactory system during mating. We show that both neuromodulators are implicated in regulating sex-specific behaviour and central nervous processing of olfactory signals.