Regulation of Life-long Neurogenesis
New neurons are born throughout life in the brains of many organisms, including humans. My laboratory’s primary focus is understanding the sequence of events that leads to the production of new nerve cells, and the regulatory events that influence this process. Our current work asks how environmental signals influence electrical and chemical signals in the brain, thereby altering the production or differentiation of new neurons. Using the crustacean brain as our experimental model, we have defined the roles of serotonin, nitric oxide, the day-night cycle and dominance status in the these events. We also have identified the stem cells that produce the new neurons, and the migratory pathway followed by the newborn cells. Our studies test how environmental (day-night cycle; tides; diet), behavioral (locomotion; social interaction) and endogenous (hormones; serotonin; melatonin; electrical activity in the brain) signals result in the selective activation of neuronal and molecular pathways controlling neurogenesis.
|Regions in the crayfish brain are labeled with dextran coupled with micro-ruby and micro-emerald dyes.||The tract-tracing dye DiI is used to trace projections from regions in the crayfish brain.|
2. Current Student Projects
Suzanne Forrest (’06) is examining the influence of strobe light on the rate of neurogenesis and locations of newborn neurons in adult crayfish brain.
Maria Genco (’06) is using miniature transponders glued to the backs of crayfish to record locomotory activity patterns. These “mini-mitters”, connected to a remote computer, will allow Maria to correlate the animals’ movements with the day-night cycle and with levels of neurogenesis.
Do-Quyen Pham (’06), working with Nancy Kolodny in the Chemistry Department, is using MRI techniques to examine the response of the olfactory pathway after (1) stimulation of the olfactory sensory receptors with taurine, and (2) ablation of the antennule containing these receptors.
Jane Rodgers (’06), working with Nancy Kolodny in the Chemistry Department, is using MRI techniques to test whether manganese can be utilized as a neural activity marker in the crayfish brain. She is doing this using photic stimulation of crayfish while in the MRI tube, to see whether the visual pathway is differentially enhanced.
3. Future Directions
In addition to the topics reviewed above, we are also developing the crustacean brain as a model for environmental toxicology. Because neurogenesis is life-long in many animals, this process may be particularly sensitive to environmental toxins. In order to explore this possibility, we are testing how organophosphate pesticides influence the birth and differentiation of new neurons, and expect that the crustacean brain will provide a very sensitive assay for the effects of toxic substances in the nervous system.