Evidence for the association of FMRFamide-related peptides with the spermatheca of Locusta migratoria

Abstract

The association of FMRFamide-related peptides (FaRPs) with the spermatheca of Locusta migratoria was demonstrated using radioimmunoassay and immunohistochemical techniques. The physiological effects of various FaRPs on the neurally evoked contractions of the spermatheca were also examined. FMRFamide-like immunoreactivity (FLI) was demonstrated in processes and cell bodies situated in the VIIIth (terminal) abdominal ganglion. These included an anterior, central and posterior pair of ventral cell bodies positioned near the midline of the ganglion, in addition to two bilaterally paired dorsal cell bodies in the posterior region of the VIIIth abdominal ganglion. Two axons displaying FLI proceed down the ventral ovipositor nerve (VON) and into the receptaculum seminis nerve which innervates the anterior regions of the spermatheca. FLI was also noted in processes on the spermathecal muscle with the highest density occurring on the spermathecal sac and coil duct. FaRPs applied to the spermathecal muscle included GQERNFLRFamide, NFIRFamide, ADDRNFIRFamide, YGGFMRFamide, FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide (PDVDHVFLRFamide). Dose-dependent physiological effects were only noted for FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide. FMRFamide led to a dose-dependent increase in the amplitude of neurally evoked contractions with a threshold of approximately 5 × 10 −7 M. SchistoFLRFamide, and ADVGHVFLRFamide, had an inhibitory effect, decreasing the amplitude of neurally evoked spermathecal contractions.