Role of biogenic amines in the postmating inhibition of pheromone sensitivity in a moth.

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

Tutzing, Alemania

Conferencia; Insect Brain and Control of Behaviour, Kleinsthirnkonferenz; 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 physiological 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 males of the noctuid moth Agrotis ipsilon, a transient post-mating inhibition of behavioural and central nervous responses to sex pheromone has been observed. 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. We combined behavioural studies, intracellular recording techniques and biochemical methods to investigate the role of the biogenic amines octopamine (OA), dopamine (DA) and serotonine (5HT) in the plasticity of the olfactory system during mating. We show that all three neuromodulators are implicated in regulating sex-specific behaviour and central nervous processing of olfactory signals. Intracellular recordings of the antennal lobe interneurons show an enhanced sensitivity to the sex pheromone blend in post-mated animals treated with biogenic amines as compared with non-treated post-mated males. The orientation response of this group remained low, although the flight activity is notably increased by the OA, DA and 5HT. In summary, biogenic amines seem to act at the central level by increasing the sensitivity to the pheromone in males that exhibit a post-mating inhibition, thus leading to an increase of the general flight activity.