The distribution and partial characterization of FMRFamide-related peptides in the salivary glands of the locust, Locusta migratoria

The distribution and partial characterization of FMRFamide-related peptides in the salivary glands of the locust, Locusta migratoria, were investigated by means of immunohistochemistry, radioimmunoassay and reversed-phase high performance liquid chromatography. Whole-mount preparations of glands stained positively against anti-FMRFamide antisera, and contained the equivalent of 837 +/- 80 fmol FMRFamide/gland pair, as determined by radioimmunoassay. FMRFamide-like immunoreactivity occurred in the processes of the transverse nerves of both the prothoracic and mesothoracic ganglia, but was not found in the salivary motoneurons 1 or 2 of the suboesophageal ganglion, both of which directly innervate the salivary glands via the salivary nerve 7b; nor was it found within the salivary nerve 7b itself, leading to the salivary glands. It was, however, found as a superficial nerve plexus on the surface of nerve 7 at the suboesophageal ganglion, but did not appear to extend to the salivary glands. The origin of this staining is unclear. High performance liquid chromatography of salivary gland tissue extracts, monitored by radioimmunoassay, revealed 4 peaks of immunoreactive material, 2 of which co-migrated with AFIRFamide and GQERNFLRFamide, previously isolated from the locust ventral nerve cord. These 2 synthetic peptides did not elevate basal levels of the second messengers cyclic AMP or cyclic GMP in the salivary glands.