Neural basis of mating-dependent olfactory plasticity in a male moth.

BARROZO RB, JARRIAULT D, GADENNE C, ANTON S.

Goettinghen, Alemania

Congreso; 8th Goettinghen Meeting of the Germarn Neuroscience Society; 2009

Most animals, including insects, have developed different strategies and mechanisms to recognize relevant information in a changing environment. External factors, including experience with a sensory stimulus, as well as the physiological state of an animal might directly influence their behaviour. Evidence is accumulating that insects, through neuronal plasticity, have developed a variety of mechanisms that allow them to modulate their behaviour. The insect olfactory system is an attractive model for the study of neuronal wiring and information processing underlying behavioural plasticity, because of well-defined stimuli and a relatively simple and accessible peripheral and central nervous system, which shares nevertheless important features with the vertebrate system. In moths, the sensitivity to sex pheromone may vary according to the time of the day, age, mating status, as well as experience1. Male moths of Agrotis ipsilon (Lepidoptera: Noctuidae) are no longer attracted to the female sex pheromone following mating2. This plasticity is not only seen at the behavioural level, but is accompanied by a change in the sensitivity of central olfactory neurons. The loss of sensitivity after mating is restored during the next day2. This transient neuronal plasticity serves as an energy-saving strategy by switching off the olfactory system and therefore preventing males from mating unsuccessfully. In the present study, we analyzed the response pattern of peripheral and central neurons to sex pheromone in virgin and newly mated A. ipsilon males, by extracellular recordings of antennal receptor neurons and intracellular recording and staining of antennal lobe neurons. Detailed analysis of the recorded activity of the different neuron types will allow us to understand how the neural network is remodelled/modulated in order to change the sensitivity of the olfactory system. In addition, we investigated whether mating might also affect the central processing of non-pheromonal odour information (i.e. plant volatiles). By analyzing the sensitivity threshold, the instantaneous firing rate, the total number of spikes during a response, as well as the latency and the duration of the response, we could show how mating changes the central processing of pheromonal information, whereas the input at the peripheral level (i.e. responses of pheromone receptor neurons) remains constant. Moreover, we show that this mating-dependent neuronal plasticity is restricted to the sex-specific pheromonal system and does not affect the processing of general odours such as plant-volatiles. 1. Anton et al 2007. Ent. exp. appl. 123:1-11. 2. Gadenne et al 2001. Proc R. Soc. London B. 268:1631-5