title: Inhibition of Manduca sexta corpora allata in vitro by a cerebral allatostatic neuropeptide.
abstract: When an in vitro assay system and radioimmunoassays specific for juvenile hormones (JH) I and III were used to probe the effect of day 4 last instar larval brains on JH synthesis by day 0 last instar larval corpora allata (CA) of the tobacco hornworm, Manduca sexta, a selective inhibition of JH I synthesis by the CA was observed. The nature of this inhibition suggested the presence of an allatostatin specific for the synthesis of JH I. Its occurrence in the day 4 brain was demonstrated by the ability of a crude brain extract to inhibit the CA in a dose-dependent manner. The allatostatic factor (ASF) appears to be a protein, based on its heat lability and pronase sensitivity, and it has apparent molecular weights of 6.8 and 13 kDa. Inhibition of JH I synthesis occurs within 1 min of exposure of the CA to the factor and is reversible by 6 h after this exposure. Thus it appears that a cerebral neuropeptide specifically inhibiting JH I synthesis by the CA is present in Manduca on day 4 of the last larval instar, a time when the hemolymph titer of JH must drop to ensure the occurrence of pupal commitment.
mesh_terms: D000818:Animals; D003335:Corpora Allata / Q000187:drug effects / Q000502:physiology*; D007605:Juvenile Hormones / Q000096:biosynthesis*; D007814:Larva; D007915:Lepidoptera / Q000502:physiology*; D009036:Moths / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology*; D009490:Neurosecretory Systems / Q000502:physiology*; D009924:Organ Culture Techniques; D012717:Sesquiterpenes / Q000096:biosynthesis
chemical_list: D007605:Juvenile Hormones; D009479:Neuropeptides; D012717:Sesquiterpenes; C008442:juvenile hormone I