Immunocytochemistry of sequence-related neuropeptides in Drosophila.

Based on structure, activity, and expression, the Drosophila drosulfakinin I peptide (DSK I; FDDY(OSO3H)GHMRFamide) is similar to the vertebrate peptide, cholecystokinin. Dromyosuppressin (DMS; TDVDHVFLRFamide) is an abundant peptide isolated from adult Drosophila which shares a high degree of sequence homology with peptides isolated from chicken, cockroach, fleshfly, and locust. DSK I and DMS, encoded by different precursors, have similar expression patterns in larval brain tissue; each localizes to cells in the anterior and medial protocerebrum. Because of the precedence for coexistence of neural messengers, it was of interest to determine the cellular expression patterns relative to one another. The question of whether the two peptides were expressed in the same cells was resolved using an immunofluorescent double-labeling technique developed for sequence-specific antisera raised in separate animals of the same species. Double labeling was done using a combination of indirect and direct immunofluorescence. DSK I and DMS were shown to localize to different cells in close proximity to one another in the larval brain. The non-overlapping expression patterns of these peptides illustrate the complete lack of cross-staining with this technique.