Antibodies generated against
bombyxin and
prothoracicotropic hormone (PTTH) of Bombyx mori and
allatotropin,
allatostatin, and
diuretic hormone (DH) of Manduca sexta react with distinct sets of cells in the central nervous system of Drosophila larvae, pupae, and adults. Brain neurons immunoreactive with
antibodies to
bombyxin, PTTH, and DH are in strikingly similar positions to their lepidopteran counterparts, indicating that at least some Drosophila neuroendocrine cells are homologous to those of lepidopterans.
Allatotropin and
allatostatin-immunopositive neurons of Drosophila differ from those of lepidopterans, but many of them are identical with neurons that express the
FMRFamide gene.
Antibodies to
bombyxin, PTTH,
allatostatin, and DH also
stain axons and axon terminals in the neurohemal part of the ring gland, and all tested
antibodies except that against
bombyxin show positive reaction in the neurohemal area of the ventral
ganglion. Although immunoreactivity with all
antibodies is variable during development, the highest levels of staining are found at developmental stages when the
neuropeptides would be expected to be functioning. A genetic analysis of
neuropeptide expression and function has been initiated by analyzing immunoreactivity in mutants that have prolonged larval life associated with imaginal disc overgrowth. Two of these mutants, dlg and dco, show abnormally strong immunoreactivity for
allatotropin during the extended larval period and the former also show increased staining with the PTTH antibody. The reduced
ecdysteroid titer and delayed or blocked metamorphosis in the mutants may be a result of altered
neuropeptide production, which is probably secondary to the imaginal disc overgrowth.