The corpora allata (CA) of insects are endocrine glands whose products, a family of juvenile hormone homologs (JHs), play a major role in the control of postembryonic development and reproduction. The CA of Lepidoptera such as the tobacco hornworm, Manduca sexta, are directly innervated by axons of cerebral neurosecretory and ordinary neurons, and it has been postulated that nervous and/or neuroendocrine regulation of the CA controls fluctuations in titers of at least three structural homologs of JH. The use of an in vitro system with radioimmunoassays to monitor the effects of neural factors on the synthesis of specific JH homologs has enabled the identification of two cerebral neuropeptides: a JH III allatotropic factor (JH III ATF), which specifically stimulates the synthesis of JH III, and a JH I allatostatic factor (JH I ASF) which inhibits the synthesis of JH I. Both these neuropeptides affect the synthesis of JH acids as well as JHs, the acids of the homologs being the products of the CA after day 2 of the last larval instar. The JH III ATF has thus far been partially purified by HPLC, and its neurosecretory cell (NSC) source localized within the brain. Its effect on the CA appears to be mediated by cAMP and extracellular calcium. cAMP is also involved in the inhibitory effect of the JH I ASF. The proposed research continues a multidisciplinary investigation of the biology of these neuropeptides regulating CA activity. Effort will continue on the establishment of purification protocols for the two characterized factors, employing HPLC methodologies. Immunological probes (antibodies) will be generated to partially purified factors and to the NSC which are their sources, in order to verify their function in vivo and to investigate their ontogeny, synthesis, transport, and release. To extend these studies to other factors regulating the synthesis of the different JHs and their acids: 1) a JH I ATF identified in studies on the interendocrine regulation of CA activity by 20-hydroxyecdysone will be characterized and its purification initiated and 2) JH II specific antiserum will be generated for use in a JH II RIA, with which factors controlling the synthesis of this homolog can be identified. The information from these studies should provide basic information about the paracrine regulation of endocrine glands by a neuroendocrine system which governs developmental processes and may also suggest new biological approaches to the of insect pests.