Nadph-diaphorase activity in corpus allatum cells of the cockroach, Diploptera punctata

Using the fixation insensitive NADPH-diaphorase reaction as a histochemical marker for the enzyme nitric oxide synthase (NOS), we investigated the pos sible sites of putatively NOS-related NADPH-diaphorase in the brain and ret rocerebral complex of the cockroach, Diploptera punctata. In the cerebral g anglion, NADPH-diaphorase expression was localized in antennal lobes, optic lobes, mushroom bodies and neurosecretory cells. The highest NADPH activit y was detected in the corpora allata (CA). Spectrophotometric quantitation indicated that NADPH-diaphorase activity first increased and then decreased (cycled) in the CA of mated females, In addition, during the first ovarian cycle, NADPH-diaphorase activity fluctuated concurrently with cyclic chang es in the size of corpus allatum cells. In virgin females, NADPH-diaphorase activity remained at a low level, but it increased if the neural connectiv es between CA and brain were severed, indicating that the brain inhibited N ADPH-diaphorase expression in the CA. Although nerve terminals were abundan t in the CA, NADPH-diaphorase was clearly endogenous and synthesized by gla ndular cells, as was shown by histochemical staining of the cytosol in all dissociated cells of the CA. We have also demonstrated NADPH-diaphorase act ivity in the CA of the American cockroach Periplaneta americana, the house cricket Acheta domesticus, the lepidopteran Leucania loreyi, and the fruit fly Drosophila melanogaster, suggesting that NOS occurs in the CA of most, if not all insects. It is therefore possible that corpus allatum cells rele ase NO, along with juvenile hormone, which presumably can function as a mes senger molecule. (C) 2000 Elsevier Science Ltd. All rights reserved.