The association of proctolin with the spermatheca of the locust, Locusta migratoria

Abstract

The association of proctolin or a proctolin-like peptide with the spermatheca of Locusta migratoria has been shown using immunohistochemistry and RP-HPLC coupled to the sensitive locust oviduct bioassay. Immunohistochemistry reveals that a proctolin-like peptide is present in processes and terminal arborizations on the spermatheca, in axons of the nerves which project to the spermatheca and in neurons in the eighth abdominal ganglion. The spermatheca of Locusta is sensitive to proctolin, with exposure to proctolin resulting in dose-dependent increases in muscle tonus as well as increases in amplitude and frequency of phasic contractions. The threshold for proctolin's effect is approximately 10 −9 M with a maximum at approximately 5 × 10 −8 M. The effects of proctolin on contractions of the spermatheca are reversible. The results indicate that proctolin, or a very similar peptide, is associated with the spermatheca of the locust Locusta migratoria and may play a neural role in modulating muscular activity.