Professor of Neurobiology and Physiology

Ph.D. 1978, State University of New York

Development and hormonal regulation of neurons and neural circuits

People in the Levine laboratory are united by a common interest in the development and function of motor systems. We approach questions of relevance to all nervous systems by exploiting the powerful molecular and genetic tools that are available in the insect, Drosophila, as well as the advantages afforded by larger insects for studies involving electrophysiology.

During metamorphosis, many of the neurons that participate in larval behavior persist to become incorporated into the neuronal circuits of the adult. To accommodate changes in behavior, these neurons modify their dendritic structures, synaptic interactions, and biophysical properties. One goal of the laboratory is to understand the behavioral relevance of such changes by following the metamorphic fates of identified neurons and the circuits in which they are involved. For example, some motoneurons of the larva that participate in crawling survive the degeneration of their target muscles to innervate new adult muscles that participate in walking behavior, whereas others persist to innervate new flight muscles of the adult. In other cases, such as the neurons that control adult heartbeat in Drosophila, novel circuits are formed. Structural modifications, such as the growth of new dendrites and axonal ramifications, and functional changes, such as alterations in membrane currents and synaptic connectivity by the motoneurons, are linked to the development and production of new behavior.

A second goal is to characterize the molecular and cellular pathways through which these developmental changes are regulated and mediated. For example, we have shown that the steroid hormone, 20-hydroxyecdysone (20E) directs the reorganization of circuits during metamorphosis by inducing the growth of new neuronal processes and the formation of new synaptic connections that are important for new components of behavior, thereby providing a useful model for examining the basic mechanisms underlying comparable steroid-mediated alterations in more complex nervous systems. We are investigating the molecular pathways through which steroid hormones and neuronal activity regulate dendritic growth and ion channel expression through the use of mutant and transgenic animals. A wide range of experimental approaches, including intracellular and patch-clamp recording, confocal microscopy and immunocytochemistry both in vivo and in cell culture, are used to address these fundamental questions.

Selected Recent Publications