ROBERTS, S.P.*; WANG, X.; GREEN, D.S.; DE BELLE, J.S.; Univ. of Nevada Las Vegas; Univ. of Nevada Las Vegas; Univ. of Nevada Las Vegas; Univ. of Nevada Las Vegas: Stress-Induced Disruption of Brain Development and Learning Ability In Drosophila

Environmental stress exposure (nutritive, chemical, electromagnetic and thermal) has been shown to disrupt CNS development in every model system studied to date. However, few studies have linked environmental stress to critical targets in brain development and their consequences for behavioral domains. Here we address this issue by examining the effects of thermal stress on development of the Drosophila melanogaster mushroom body (MB), a highly conserved paired neuropil structure in the insect brain that is important for associative learning. Previous research has shown that Drosophila MB development is sensitive to exposure to the cytostatic drug hydroxyurea, which leads to a profound loss of MB volume in adult flies. These MB-less flies respond to odors but are unable to form memories of odors paired with electric shocks. In this study, 25 �C-reared D. melanogaster were exposed daily to a brief heat shock (39.5 �C for 40 min) throughout larval and pupal development. MB volume was reduced by roughly 40%, yet the central complex (a central brain structure involved in motor control), wings and legs showed little or no reduction in size relative to control flies reared at a constant 25 �C. MBs were sensitive to heat shock and reduced following heat treatment during all stages of larval and pupal development, with each type of Kenyon cell (born sequentially in different developmental stages) reduced either in number or in size, suggesting that heat is probably exerting disruptive effects on MB precursor neuroblasts or ganglion mother cells. Heat shock during sub-adult development did not affect adult olfaction or electrical shock avoidance, but profoundly reduced the ability of adult flies to form both short-term and long-term memories.