9709514 BELTZ Dr. Beltz will investigate two related issues of neuronal development and plasticity in the lobster brain. One area of this research builds on recent studies in a variety of organisms that point to the potential contibution of proliferating cells that generate new neurons in the adult brain. The birth of new neurons in the mature olfactory pathway of the lobster has been demonstrated both in the receptor population and in interneurons that are involved in olfactory processing and transmission of information to higher centers. Integration of new cells into existing circuits may provide a means of modifying olfactory learning or integration in the mature brain. The proposed studies will examine the possible regulation of neurogenesis by steroid hormones and other factors, such as damage to the antennules in the olfactory periphery. The possible contribution of neuronal death ("apoptosis") to the refinement of the mature olfactory system also will be addressed. The second set of studies will examine the role of the neurotransmitter serotonin in brain development. In contrast to the apparent gradual changes in cellular components of the olfactory pathway, the serotonergic input to the olfactory system appears to be very stable in lobsters. Identified serotonergic interneurons innervating the olfactory lobes appear early in embryogenesis and persist throughout larval and adult life. Serotonin depletion during the embryonic period results in a dramatic slowing of growth in olfactory target regions. This implies that serotonin normally promotes the growth of these regions. In future studies the cellular bases of this growth retardation will be investigated by comparing the development of specific groups of olfactory interneurons exposed to reduced, normal and increased levels of serotonin. These studies are relevant to developmental mechanisms in higher organisms because there are many parallels between the organization of olfactory pathways and processing even in phylogen etically distant species. In addition, these studies will explore basic mechanisms involved in the development and maintenance of neural circuits which may be applicable in a spectrum of other organisms.
