Imaging Odor Coding and Synaptic Plasticity in the Mammalian Brain with a Genetically Encoded Probe

MCGANN, JOHN P.; PÍREZ, NICOLÁS; WACHOWIAK, MATT

New York, Estados Unidos

Conferencia; 28th IEEE EMBS Annual International Conference; 2006

IEEE Engineering in Medicine and Biology Society

We have used genetically-encoded fluorescent activity indicator synaptopHluoring (spH), expressed selectively in mouse olfactory receptor neurons, to image odor representations at the input and output of the olfactory bulb. The olfactory bulb is a powerful system for in vivo fluorescence imaging because its inputs are segregated into receptor-specific functional units (glomeruli) that are optically accessible and receive massively convergent input from sensory neurons.  In a line of transgenic mice expressing the genetically encoded fluorescent exocytosis indicator synaptopHluorin (spH) under the control of a receptor neuron-specific promoter (OMP), odorant-evoked patterns of receptor neuron input to ~ 10% of the olfactory bulb can be imaged with excellent spatial resolution and sensitivity with single brief odorant presentations. Odor representations are similar across mice and can be imaged repeatedly in the same animal for months. We have also used OMP-spH to monitor the modulation of transmitter release from receptor neurons both in vivo and in slices. In slices, shock-evoked spH signals are rapid and linear reporters of transmitter release, although control for changes in extracellular pH is critical for proper interpretation of the spH signal. These features have allowed us to characterize the functional organization of presynaptic modulation at the first olfactory synapse.  The capacity for long-term chronic imaging permits the direct visualization of the function regeneration and remapping of input to the olfactory bulb after lesions of the nasal epithelium.