Inhibitory role of ecdysone on neurogenesis and polyamine metabolism in the adult cricket brain

Abstract

Persistent neuroblasts that continue to produce interneurons were discovered in the mushroom bodies of the adult house cricket, Acheta domesticus (Cayre et al., 1994). In the present work, we examine the influence of ecdysone on this neurogenesis. In control females, the mitotic index decreased concomitantly to the rise of ecdysteroid titer, which accompanied oocyte maturation, whereas it remained unchanged in ovariectomized females. Furthermore, ecdysone injection into ovariectomized animals had a significant inhibitory action on neuroblast mitotic activity. Since cell proliferation and neuronal diferentiation have been shown to be affected by polyamines, we also studied the action of ecdysone on polyamine metabolism. Ovariectomy induced a decrease in polyamine levels of fat body and markedly increased brain spermidine levels. In neural tissue, ecdysone injection into ovariectomized females reduced spermidine levels to control values. Our results suggest that adult cricket brain is a target for ecdysone action. Moreover, the tight correlation we demonstrated between neurogenesis and polyamine titers underlines the possible involvement of polyamines in neuroblast proliferation. Arch. Insect Biochem. Physiol. 35:85–97, 1997. © 1997 Wiley-Liss, Inc.