ON THE CONTROL OF ECDYSONE BIOSYNTHESIS BY THE CENTRAL-NERVOUS-SYSTEMOF BLOWFLY LARVAE

Ecdysone was found to be the major secreted steroid of ring glands dis sected from blowfly larvae and incubated in vitro. Other secretory pro ducts such as 3-dehydroecdysone and 20-deoxy-makisterone A could not b e detected when the glands were labelled with tritiated cholesterol. E cdysone synthesis and secretion were found to be tightly coupled. The highest rate of secretion was observed a few hours before pupariation. In vitro, the rate of ecdysone secretion by ring glands was affected significantly by coincubation with the central nervous system (CNS). M odulating effects from the CNS to the gland were mediated both by cult ure medium and by nerve connections. Distinct parts of the CNS reveale d multiple and partially opposite effects on ecdysone secretion, sugge sting a more complex control than had been anticipated. Multiple neura l control systems appear to be involved. Moreover, the observed effect s changed with development during the second half of the third instar, reflecting a significant plasticity of neural control. (C) 1993 Wiley -Liss, Inc.