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Focus group: Multicomponent synergies in chemoreception

Rapporteur: Tristram Wyatt

Abstract

Synergy describes the phenomenon when any one component of a multicomponent pheromone shows little or no activity by itself and only the complete mixture has an activity comparable to the natural pheromone. It is to be expected from multicomponent pheromones and may be a natural outcome of the combinatorial way they are processed in the brain of both vertebrates and invertebrates.

Synergy is to be expected from multicomponent pheromones, which gain their specificity by the combination (above). I would suggest that synergy is a natural outcome of the way multicomponent pheromones are processed in the brain. It reflects the combinatorial organization of olfaction (see Chapter 9). For example, in the male moth, the message“fly upwind” in response to female pheromone is only sent to the higher brain if all the correct molecules stimulate their antennal olfactory sensory neurons and the glomeruli in the brain to which these lead (Chapter 9) (Hauptet al. 2010). The neural circuits can be thought of as acting like digital logic “AND” gates: if a component is missing or at the wrong ratio, the stimulus does not go higher in the brain. Conversely, the circuit gives a “STOP” if there is activation of olfactory sensory neurons sensitive to a pheromone component of the wrong species (e.g., Lelitoet al. 2008). Nematode multicomponent pheromones are processed by simpler circuits, without glomeruli, but on these same principles.