Dual effect of ecdysone on adult cricket mushroom bodies

Abstract

Mushroom bodies, which are the main integrative centre for insect sensorial information, play a critical role in associative olfactory learning and memory. This paired brain structure contains interneurons grouped in a cortex, sending their axons into organized neuropiles. In the house cricket (Acheta domesticus) brain, persistent neuroblasts proliferate throughout adult life. Juvenile hormone (JH) has been shown to stimulate this proliferation [Cayre, M., Strambi, C. & Strambi, A. (1994) Nature, 368, 57-59]. In the present study, the effect of morphogenetic hormones on mushroom body cells maintained in primary culture was examined. Whereas JH did not significantly affect neurite growth, ecdysone significantly stimulated neurite elongation. Moreover, ecdysone also acted on neuroblast proliferation, as demonstrated by the reduced number of cells labelled with 5-bromodeoxyuridine following ecdysone application. Heterospecific antibodies raised against ecdysone receptor protein and ultraspiracle protein, the two heterodimers of ecdysteroid receptors, showed positive immunoreactivity in nervous tissue extracts and in nuclei of mushroom body cells, indicating the occurrence of putative ecdysteroid receptors in cricket mushroom body cells. These data indicate a dual role for ecdysone in adult cricket mushroom bodies: this hormone inhibits neuroblast proliferation and stimulates interneuron differentiation. These results suggest that a constant remodelling of mushroom body structure could result from physiological changes in hormone titres during adult life.

Ecdysone signaling regulates the formation of long-term courtship memory in adult Drosophila melanogaster

“…The ability of ecdysone to remodel the nervous system is known not to be limited to developmental stages. For example, in the adult house cricket (Acheta domesticus) brain, ecdysone has been shown to inhibit proliferation of neuroblasts in the MBs and to trigger their differentiation into interneurons (50). Although there is no evidence of continued neurogenesis in the adult Drosophila brain, it is possible that ecdysone signaling induces significant changes in properties of existing neurons, resulting in structural and functional remodeling of neuronal circuits.…”

The Steroid Molting Hormone Ecdysone Regulates Sleep in Adult Drosophila melanogaster

“…It has been shown in Drosophila that ecdysone controls neuronal remodeling during formation of the adult nervous system and that it does so through signaling pathways involving EcRs and TGF-b (Kraft et al 1998;Lee et al 2000;Zheng et al 2003). Ecdysone also plays a role in remodeling of the adult brain in the house cricket (Acheta domesticus), in this case by inhibiting neuroblast proliferation in the MBs and triggering their differentiation into interneurons (Cayre et al 2000). In honeybees (Apis mellifera L.), ecdysone exposure activates an EcR-mediated transcriptional cascade in the adult MB neurons, suggesting that ecdysone is important for reorganization of the adult brain (Velarde et al 2009).…”

Reproductive ground plan may mediate colony-level selection effects on individual foraging behavior in honey bees

“…In addition to their gonotrophic role, these hormones govern shifts between behavioral states in the reproductive cycle, e.g., by controlling the shift from nectar to blood-host foraging in female Culex nigripalpus mosquitoes (52), the shift from feeding and sexual behavior to fasting and parental activity in the earwig Labidura riparia (53), the initiation of oviposition in crickets (54), the initiation of sexual behavior of male Agrotis ipsilon moths (55), and shifts between periods of intense flight activity and reproductive behavior in several taxa (34). JH and ecdysteroids affect adult behavior by regulating the growth and central processing of sensory and motor neurons (26,(56)(57)(58)(59), and their coordinated regulatory modes have been shown to result in synchronized changes in sensory perception, locomotor activity, and reproductive physiology (26,60).…”