Functional roles of neuropeptides in the insect central nervous system

With the completion of the Drosophila genome sequencing project we can begi n to appreciate the extent of the complexity in the components involved in signal transfer and modulation in the nervous system of an animal with reas onably complex behavior. Of all the different classes of signaling substanc es utilized by the nervous system, the neuropeptides are the most diverse s tructurally and functionally. Thus peptidergic mechanisms of action in the central nervous system need to be analyzed in the context of the neuronal c ircuits in which they act and generalized traits cannot be established. By taking advantage of Drosophila molecular genetics and the presence of ident ifiable neurons, it has been possible to interfere with peptidergic signali ng in small populations of central neurons and monitor the consequences on behavior. These studies and experiments on other insects with large identif iable neurons, permitting cellular analysis of signaling mechanisms, have o utlined important principles for temporal and spatial action of neuropeptid es in outputs of the circadian clock and in orchestrating molting behavior. Considering the large number of neuropeptides available in each insect spe cies and their diverse distribution patterns, it is to be expected that dif ferent neuropeptides play roles in most aspects of insect physiology and be havior.