This study is designed to determine whether interactions between different types of neurons direct or influence the structural and functional reorganization that takes place in the nervous system during postembryonic development. In both vertebrates and invertebrates motor circuits undergo structural and functional changes after birth or hatching. Cell-cell interactions, as well as humoral signals, such as steriod hormones, have been implicated in influencing these postembryonic changes, but the respective contributions of hormonal signals and cell-cell interactions to neuronal differentiations in hormonally-sensitive systems have not been well-defined. This study will utilize an insect in order to examine the influence of cell-cell interactions at the level of individual neurons during hormonally-controlled metamorphosis. The study will be centered around a previously identified motor neuron that is present at both larval and adult stages but undergoes extensive remodeling of its dendritic processes during memtamorphosis. Dr. Kent's objectives are to identify the interactions that differentially affect the motor neuron in specific regions of its dendritic arbor. Surgical manipulations and the use of mutant phenotypes will help identify the specific classes of neurons that shape or regulate dendritic growth. Electrophysiological and anatomical methods will be employed to identify and characterize individual neurons that influence dendritic morphology of the identified motor neuron. Information gained by these studies will not only increase our understanding of the relative contributions of cell-cell interactions and hormonal siganls to dendritic changes in a hormonally-sensitive system, but will contribute in a broader sense to an understanding of basic developmental mechanisms.
