John Hildebrand

Professor, Neuroscience
Regents Professor
Professor, Chemistry and Biochemistry
Professor, Molecular and Cellular Biology
Professor, Entomology / Insect Science - GIDP
Professor, Neuroscience - GIDP

My group conducts research that combines anatomical, behavioral, chemical, and neurophysiological methods in a multidisciplinary approach to problems of the organization, physiology, functions, and postembryonic development of the insect nervous system. The main goal of this work is to discover fundamental principles and mechanisms common to many or all nervous systems through studies of the experimentally favorable nervous systems of insects. In view of the importance of insects in their own right, we also aim to contribute to knowledge that will help to alleviate the harm done by insects that are predators of the human food supply or vectors of diseases. Areas of our principal interest currently include: the physiology, functional organization, and postembryonic development of the olfactory system; sensory control of mating behavior and insect-host interactions, including feeding and oviposition behaviors; chemical ecology and behavioral aspects of moth-hostplant interactions; olfactory learning and the roles of biogenic amines in plasticity of olfactory function; and functional organization of neurosecretory systems. Functional organization and physiology of the insect olfactory system. We study the olfactory system of the giant sphinx moth Manduca sexta. Using intracellular and staining methods, extracellular and multi-unit recording techniques, and pharmacological manipulations, we explore the neuronal circuitry and synaptic interactions in the antennal lobe (AL), the primary olfactory center in the moth's brain. We also use histological and neuronal tracing methods to learn about the anatomical organization of the AL and its sensory inputs. Our goal is to understand cellular mechanisms of information processing in the olfactory pathways in the CNS. Much of our work has focused on the sexually dimorphic olfactory subsystem in the male moth that is specialized to detect and process information about the female's sex pheromone. We also conduct multi-level studies of the detection and central processing of information about volatile compounds emitted by living plants. In addition to our primary focus on the AL, we are very interested in the higher-order olfactory pathways in the protocerebrum that are involved in processing of the outputs of the ALs and their integration with information of other modalities. Postembryonic, metamorphic development of the olfactory system. We have long been interested in neural development and plasticity in the ALs during the postembryonic development of Manduca. We have shown that certain, sexually dimorphic glomeruli characteristic of male and female ALs develop only if the AL is innervated, respectively, by axons of genetically male or female olfactory receptor cells. In a continuing collaboration among members of my group and faculty colleagues Leslie Tolbert, Lynne Oland, Alan Nighorn and their coworkers, a multidisciplinary quest for the cellular and molecular mechanisms underlying these and other aspects of AL development is in progress. Behavior and chemical ecology. In parallel with our studies of the olfactory system of Manduca, we are investigating the chemical composition of the volatiles emitted by living host- and nonhost plants and using a variety of chemical, physiological and behavioral methods to identify behaviorally significant compounds in those complex mixtures. In addition, we are exploring the roles of CO2 in moth-plant interactions, and we conduct detailed studies of the effects of odors on the behavior of flying Manduca in the field and in laboratory wind tunnels. Organization and functions of neurosecretory systems. We have a long-standing interest in the identification, metabolism, and cellular localization of neuroeffectors (e.g. neurotransmitters, neuromodulators, neurohormones) in insects. Our current efforts focus on the functional organization of neurosecretory cells in the CNS that express neuropeptides and polypeptide neurohormones and on the roles of such cells in the control of organ function and behavior of the insect.