Effect of tyramine and stress on sex-pheromone production in the pre- and post-mating silkworm moth, Bombyx mori

Tyramine (TA) increased significantly after mating, whereas there were no significant differences in octopamine (OA) and dopamine (DA) levels in the brain–suboesophageal ganglion (SOG) complexes between virgin and mated females. The effects of various biogenic amines were tested on pheromone production of virgin and mated females of the silkworm moth, Bombyx mori. After 8 h a significant reduction by TA (46%) was observed. Meanwhile, when OA or DA was injected, a significant increase of pheromone titer was observed in both virgin and mated females. This study also presents evidence for an increase in levels of OA and DA in the brain–SOG complexes in response to mechanical stress in B. mori female. TA suppressed pheromone production in an in vitro pheromone gland (PG) homogenate preparation, thus suggesting that the target of TA is the PG. TA inhibited pheromone production in vitro in a dose-dependent manner and DA had a lower inhibitory activity than TA, whereas OA had no effect, suggesting that TA is a candidate for regulating pheromone production in the PG, although other factors could be responsible for the pheromonostatic function.