Switching attraction to inhibition: a neuroethological mechanism of post-mating sexual abstinence.

BARROZO RB

Simposio; I Latin American Association of Chemical Ecology; 2010

In animals, mating involves detection and central processing of relevant chemical cues that lead to appropriate reproductive behaviours. In many species, the most prominent use of olfactory signals is the sex pheromone communication, with males generally attracted by a female-produced pheromone. Male reproductive success depends not only on the ability to locate and copulate with a female, but also on their ability to effectively transfer an ejaculate. However, males are limited with respect to the number of ejaculates they can deliver and the time required to restore depleted reserves. Although males of many species are known to enter in a refractory post-ejaculatory interval (PEI), the mechanisms that lead to this sexual abstinence are far from being understood. In the male moth Agrotis ipsilon, mating induces a transient inhibition of behavioural and central nervous responses to sex pheromone. Using non-pheromonal (plant) odours, pheromones, and their mixture, we showed that the observed lack of pheromone response originates from differential post-mating odour processing in the brain. Although mated males still respond to plant odours alone, their response to mixtures depends on the added pheromone concentration. Below a specific threshold, sex pheromone is not detected at the brain level; above this threshold, it becomes inhibitory. This PEI can thus be interpreted as a “refusal to respond”, but not as a sleep-like/exhaustion behaviour. A sex pheromone, which is generally considered as an attractant, can become inhibitory depending on the physiological state of the receiver. We provide evidence for a neuroethological mechanism based on transient odour-selective central nervous processing leading to post-mating sexual abstinence in males.