Central processing of sex pheromone stimuli is differentially regulated by juvenile hormone in a male moth

In the male moth, Agrotis ipsilon, the neuronal basis for juvenile hormone (JH)-linked modulation of sex pheromone responsiveness was investigated following stimulation of the antenna with i) an extract of female pheromone gland, ii) the synthetic pheromone blends from A. ipsilon and a closely related species, A. segetum, and iii) single components of the A. ipsilon blend. Response characteristics of olfactory interneurons were studied in the antennal lobe (AL) at different ages and with manipulated JH levels using intracellular recording techniques. Blend-specific, generalist and component-specific neurons were identified and described according to their response pattern. The proportion of low threshold AL interneurons increased significantly with age for all stimuli tested. Changes were, however, less pronounced for the minor single components. The proportion of low threshold AL interneurons in allatectomized (JH-deprived) mature males was significantly lower for all stimuli than in intact mature males. A large proportion of low threshold AL interneurons responding to the pheromone blends, but not as pronounced for single pheromone components, could be restored/induced by injecting JH either into JH-deprived mature males or into young immature males. The specificity for the species-specific blend compared to the A. segetum blend increased with age and JH injections.