Role of Hormones in the Control of Insect Behavior

University Of Washington, Seattle WA

Investigators

Abstract

To shed their old skin at the end of a molt, insects display the ecdysis sequence, a complex behavioral sequence that involves at least three discrete behavioral phases. Previous work in the moth, Manduca sexta, indicated that this behavioral sequence is organized by a circuitry of neuromodulatory neurons that control the duration of each behavioral phase and the transition from one phase to the next. One of the key neuromodulators is the neuropeptide eclosion hormone (EH), that controls the transition from the first to the second behavioral phase. EH target neurons, identified by their increased levels of the intracellular messenger cyclic GMP after EH release, include the modulatory neurons that produce the peptides needed for the last two behavioral phases. Initially, electrophysiological studies will focus on these cells and determine the relationship of their activity both to EH release and to the onset of the appropriate behavioral programs. Since there are defined environmental stimuli that are known to stimulate or suppress the transition from one behavior to the next, studies will be done to determine if and where these stimuli affect the neurons in the neuromodulatory circuit. New studies on the fruitfly, Drosophila, will then genetically dissect the neuromodulatory circuit that is involved in the last two phases of the sequence. The proper functioning of the brain requires the regulated release of neuromodulators such as neuropeptides and amines. Since these modulators play a crucial role in determining behavioral states, a key to understanding behavioral organization lies in understanding how modulatory systems are organized and how behaviorally important stimuli act on them to control neuromodulator release. The ecdysis system has become a premiere system for studying the organization of neuromodulatory circuits and how they relate to complex behavior.