1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

489 Poster Developmental, Neurogenesis, and ConsumerResearchTIME LAPSE CONFOCAL MICROSCOPY ON MIGRATINGNEUROBLASTS IN THE MOUSE ROSTRAL MIGRATORYSTREAMBovetti S. 1 , Bovolin P. 2 , Hsieh Y. 1 , Perroteau I. 2 , Puche A.C. 1 1Anatomy and Neurobiology, University of Maryland, Baltimore, MD; 2Human & Animal Biology, University of Turino, Turino, ItalyNeural progenitors cells born in the subventricular zone (SVZ)migrate along the rostral migratory stream (RMS) t the olfactory bulb,and differentiate into several classes of interneurons. Tangentialmigration in the RMS takes place in `chains´ of cells as compared toindividual cells in cortical radial migration. To examine the biophysicsof migration in this pathway we labeled SVZ progenitors with CellTracker Green (CTG) in P2 and P17 mice. At 3 days post injectionacute saggital slices were time-lapse imaged on a confocal microscope.The centroid of the cell soma was tracked for at least 60min. Individualcells in the RMS migrate in a salutatory manner with bursts of highspeed followed by periods of slower speed (mean 26-31 µm/hr).Neurotransmitters, particularly GABA, have been implicated asmodulators of neuroblasts migration in the RMS. To test the role ofGABA and glutamate in this model slices were incubated with specificagonists/antagonists. Incubation of the slices with the GABAA receptorantagonist gabazine increases the migratory speed by 45% while theagonist muscimol decreases speed of 34%. NMDA/AMPA and mGluRgroup I receptors are also expressed along the RMS; however,inhibition of these receptors does not significantly affect migration.Migratory cells can interact and modify the extracellular matrix throughexpression of a family of proteins, the matrix metalloproteinases(MMPs)., which we found expressed in the RMS. In the presence ofinhibitor neuroblasts migration in the RMS was reduced by ~35%,suggesting a role for these proteases in CNS neuroblasts migration.Supported by NIH DC005739 and Fondazione Cassa di Risparmio diCuneo.490 Poster Developmental, Neurogenesis, and ConsumerResearchODORANT DEPRIVATION REVERSIBLY MODULATESNR2B-MEDIATED CREB PHOSPHORYLATION IN MOUSEPIRIFORM CORTEXKim H.H. 1 , Puche A.C. 1 , Margolis F.L. 1 1 Anatomy and Neurobiology,University of Maryland at Baltimore, Baltimore, MDThe olfactory system is an outstanding model to characterize activitydependentplasticity in mammals. The goal of this study is to elucidatemolecular mechanisms underlying neuronal plasticity in mouse piriformcortex (PC). Although the functional organization of the olfactory bulb(OB) to PC network has been studied electrophysiologically themolecular mechanisms remain elusive. To understand the influence ofthe periphery on trans-synaptic gene regulation in the PC, we usedintranasal zinc sulfate irrigation as well as permanent and reversiblenaris occlusion. We characterized reductions in NMDA receptor NR2Bsubunit expression in OB and PC layer IIb by measuring itsimmunoreactivity and mRNA level 7 days after zinc sulfate lesion. Noevidence for neuronal death was observed after deafferentation. We alsofound the same reduction 5 days after naris occlusion, implying that thereduction in NR2B expression in PC is activity-dependent. We furtherdemonstrated an activity-dependent reduction in phosphorylation oftranscription factor CREB, which is in the NR2B-mediated signaltransduction pathway, and subsequently characterized the subset ofpyramidal cells that shows high sensitivity to odor deprivation, usingretrograde tracers. We confirmed that the activity-dependent reductionof CREB phosphorylation can be reversed by 10 days of odor reexposure.Taken together, the present results demonstrate the molecularmechanisms underlying functional organization and odor-evokedactivity-dependent neuronal plasticity of PC. Supported by NIHDC003112 (FLM) and NIH DC005739 (ACP).491 Poster Developmental, Neurogenesis, and ConsumerResearchGENESIS AND MIGRATION OF MITRAL CELLS IN THEDEVELOPING MOUSE OLFACTORY BULBHawisher D. 1 , Tran H. 1 , Gong Q. 1 1 Cell Biology and Human Anatomy,University of California, Davis, CAOlfactory sensory neurons expressing the same odorant receptorconverge their axons to the same glomeruli where they synapse withdendrites from a small group of mitral cells. It is not clear, invertebrate, whether mitral cells are genetically programmed to target thedefined glomerulus in the olfactory bulb. Mitral cells are born duringearly embryonic stages and migrate to form a single cell layer in theadult olfactory bulb. To investigate the genesis and the migration ofmitral cells, we have employed a double labeling technique to followtwo cell populations simultaneously. Two different thymidine analogs,CldUrd and IdUrd, were injected into timed pregnant mice two daysapart. Cells in S phase at time of injection will be labeled by eitherCldUrd or IdUrd and their numbers and distribution are analyzed. Wehave obtained evidence that, in contrast to the development of corticaltissue, older cells, born at E11, are pushed outward while the youngercells, born at E13, remain more central in the olfactory bulb at E15.The older cells were measured to be significantly farther away from theventricular zone than the younger cells (45.8 ± 0.74 µm versus 28.0 ±0.76 µm, p