Functional cross-reactivities of some locustamyotropins and Bombyx pheromone biosynthesis activating neuropeptide

Naturally occurring, recently isolated insect neuropeptides locustamyotropin II and III and Bombyx pheromone biosynthesis activating neuropeptide I (PBAN-I) bearing common carboxy terminals (Phe-X-Pro-Arg-Leu-NH2) were studied for possible functional crossreactivities. On a Locusta oviduct and Leucophaea hindgut bioassay, synthetic Bombyx PBAN-I caused an increase in the spontaneous contractions at a threshold of 0.6 × 10−8 and 1.45 ± 0.4 × 10−8 M, respectively. In Bombyx mori, injection of 0.001 pmol of locustamyotropin II and 0.01 pmol of locustamyotropin III/female induced bombykol production and maximal production was attained at 0.1 or 1 pmol dose, respectively. In Spodoptera litura pheromone production increased in a dose-dependent manner when 1–100 pmol of peptide was injected into females. When pheromone glands were incubated in vitro in Grace's medium containing different doses of locustamyotropin II or III, maximal sex pheromone production was induced at 5 pmol of peptide/150 μl medium in B. mori and at 15 pmol peptide/50 μl in S. litura, respectively. Present results support the idea that the common C-terminal pentapeptide (Phe-X-Pro-Arg-Leu-NH2) is responsible for both, myotropic and pheromonotropic activity.