Selective Imaging of the Receptor Neuron Population in the Olfactory Bulb of Zebrafish and Mice

Abstract

Convergence of the olfactory projections allows analysis of receptor repertoires in the olfactory bulb The neuronal processing of odors takes place in several types of neurons, including the sensory neurons, projection neurons and interneurons. To understand the neuronal representation of odors and eventually the encoding of those odors it is important to selectively measure the contributions of the different neuron populations to odor-induced neuronal activity. We are analyzing the odor responses of the population of olfactory receptor neurons in two experimental systems, zebrafish and mouse. Odor responses are measured in the receptor neuron terminals within the olfactory bulb. Thus, the response properties of many different odorant receptors can be visualized simultaneously by optical imaging of neuronal activity in the olfactory bulb, since olfactory receptor neurons expressing the same odorant receptor converge onto common neuropil structures in the olfactory bulb, the glomeruli (cf. Korsching, 2002). This transition from presumably stochastic expression of odorant receptor genes in scattered olfactory receptor neurons within the sensory epithelium to an ordered map in the olfactory bulb (Figure 1) allows a unique view on the size and composition of the receptor repertoires that are activated by particular odorants. Selective analysis of odor-induced presynaptic