Imaging odor coding and synaptic plasticity in the mammalian brain with a genetically-encoded probe

Area of Science:

• Neuroscience
• Olfactory System Research
• Sensory Biology

Background:

• The olfactory bulb processes sensory input through segregated, receptor-specific functional units called glomeruli.
• In vivo fluorescence imaging offers a powerful method to study olfactory system organization.
• Genetically-encoded indicators allow for targeted visualization of neural activity.

Purpose of the Study:

• To image odor representations at the olfactory bulb input using a genetically-encoded fluorescent indicator.
• To characterize the functional organization and presynaptic modulation of the first olfactory synapse.
• To visualize regeneration and remapping of olfactory bulb input after nasal epithelium lesions.

Main Methods:

• Utilized transgenic mice expressing synaptopHluorin (spH) in olfactory receptor neurons under the OMP promoter.
• Performed in vivo fluorescence imaging of odorant-evoked activity in the olfactory bulb.
• Analyzed spH signals in olfactory bulb slices to assess transmitter release and extracellular pH effects.

Main Results:

• Odorant-evoked patterns of receptor neuron input were imaged with high spatial resolution and sensitivity.
• Odor representations were found to be consistent across mice and reproducible over time.
• spH signals accurately reported transmitter release, with extracellular pH control being crucial for interpretation.

Conclusions:

• SynaptopHluorin imaging provides a sensitive tool for studying olfactory bulb input organization and function.
• The method allows for long-term chronic imaging to observe neural regeneration and remapping.
• Characterization of presynaptic modulation at the first olfactory synapse was achieved.