Meeting Abstract

P3.44  Saturday, Jan. 5  Ecdysis Triggering Hormone stimulates fictive pre-ecdysis and ecdysis in intermolt larval tobacco hornworm nervous systems. TAMVACAKIS, Arianna*; FUSE, Megumi; San Francisco State University; San Francisco State University ariannat@sfsu.edu

Ecdysis Triggering Hormone (ETH) is a peptide from peripheral glands lining the body wall of the tobacco hornworm, Manduca sexta. At the end of the molt, ETH has been shown to induce fictive pre-ecdysis and ecdysis bursting patterns associated with the shedding of the old cuticle in the isolated nervous system of insects (Zitnan et al, 1996). ETH reactivity has also been shown to cause fictive movements associated with those behaviors in intact molt period larvae as well as elevated cGMP in identified neurons (Zitnan et al, 1996; Gammie et al, 1997). The role of ETH during the intermolt period, however, has not been as well characterized. The beginning of the molt period is marked by a large increase in ecdysteroid titers, which has been suggested to be required for ETH activity. In vitro fictive pre-ecdysis and ecdysis behaviors were monitored electrophysiologically in response to prolonged ETH exposure at intervals after the normal molt period. Fictive pre-ecdysis and ecdysis did occur in intermolt preparations as late as 72 hours post-ecdysis, although burst characteristics and onset times were altered. In contrast, injection of ETH into similarly timed animals did not induce pre-ecdysis or ecdysis behaviors, and the cGMP response characteristic of normal molting behavior was not noted. These data indicate that ecdysteroid-induced CNS activity is not necessary for ETH stimulation of fictive pre-ecdysis and ecdysis in intermolt larvae. It also suggests that low levels of ETH receptors are sufficient for ETH activity in vitro.