Odorant Receptors Signaling Instructs the Development and Plasticity of the Glomerular Map

Abstract

The olfactory system provides a great opportunity to explore the mechanisms that underlie the formation and function of neural circuits because of the simplicity of its structure. Olfactory sensory neurons (OSNs) located in the peripheral olfactory epithelium (OE) take part in the initial formation and function of glomeruli in the olfactory bulb (OB) inside the central nervous system. Glomeruli are key in the process of transduction of olfactory information, as they constitute a map in the OB that sorts the different types of odorant inputs. This odorant categorization allows proper olfactory perception, and it is achieved through the anatomical organization and function of the different glomerular circuits. Once formed, glomeruli keep the capacity to undergo diverse plasticity processes, which is unique among the different neural circuits of the central nervous system. In this context, through the expression and function of the odorant receptors (ORs), OSNs perform two of the most important roles in the olfactory system: transducing odorant information to the nervous system and initiating the development of the glomerular map to organize olfactory information. This review addresses essential information that has emerged in recent years about the molecular basis of these processes.

Brief olfactory learning drives perceptive sensitivity in newborn rabbits: New insights in peripheral processing of odor mixtures and induction

“…In rodents, the anatomical connection between the first two stages of the olfactory system, namely ORNs and olfactory bulb glomeruli takes place very early in life and for instance ORNs respond to odorants immediately at birth ( [77] and personal observations). It has been proposed that ORN/OR activity is a prerequisite to the basal expression of ORs [78,79] and to the correct projection of the axons defining the initial glomerular map [80]. Indeed, the selective suppression of activity in a set of ORNs prevents the formation of the targeted glomeruli [81].…”

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“…Olfactory neurons with the same receptor types organize and converge onto specific glomeruli in each olfactory bulb. 23,24 First-order synapses occur in the glomeruli of the olfactory bulb. This topographic mapping allows the olfactory system to encode an almost limitless array of odors.…”