Release of neurosecretory granules within the corpus allatum in relation to the regulation of juvenile hormone synthesis in Diploptera punctata

The release of neurosecretory granules within the corpora allata (CA) of th e viviparous cockroach Diploptera punctata has been compared in glands with intact nerves from the brain (Brain-CA) and those detached from the brain. Measurements of juvenile hormone (JH) synthesis in vitro, comparing these two conditions of the CA at several stages of vitellogenesis in adult femal es, showed lower production of hormone in Brain-CA complexes than in CA alo ne. Glands treated with tannic acid to trap exocytotic granules before fixa tion for electron microscopical examination showed, in sample sections, 10 times more exocytotic profiles in the glands with intact nerves to the brai n than in the isolated glands. Sections treated with antibody against allat ostatin I (Dip 7), a member of the neuropeptide family that inhibits JH syn thesis by CA in vitro, showed neurosecretory granules in allatostatin immun oreactive nerves to be 75+/-4% of the granules in the sample of sections of CA. Because the total quantity of allatostatin in CA was found by ELISA no t to vary significantly with changes in JH synthesis, it is concluded that the lower rates of JH synthesis by glands with intact nerves to the brain a re most likely due to the release of small amounts of allatostatin within t he CA. (C) 2000 Elsevier Science Ltd. All rights reserved.