Unraveling the Role of Dopaminergic and Calretinin Interneurons in the Olfactory Bulb

Abstract

The perception and discriminating of odors are sensory activities that are an integral part of our daily life. The first brain region where odors are processed is the olfactory bulb (OB). Among the different cell populations that make up this brain area, interneurons play an essential role in this sensory activity. Moreover, probably because of their activity, they represent an exception compared to other parts of the brain, since OB interneurons are continuously generated in the postnatal and adult period. In this review, we will focus on periglomerular (PG) cells which are a class of interneurons found in the glomerular layer of the OB. These interneurons can be classified into distinct subtypes based on their neurochemical nature, based on the neurotransmitter and calcium-binding proteins expressed by these cells. Dopaminergic (DA) periglomerular cells and calretinin (CR) cells are among the newly generated interneurons and play an important role in the physiology of OB. In the OB, DA cells are involved in the processing of odors and the adaptation of the bulbar network to external conditions. The main role of DA cells in OB appears to be the inhibition of glutamate release from olfactory sensory fibers. Calretinin cells are probably the best morphologically characterized interneurons among PG cells in OB, but little is known about their function except for their inhibitory effect on noisy random excitatory signals arriving at the main neurons. In this review, we will mainly describe the electrophysiological properties related to the excitability profiles of DA and CR cells, with a particular view on the differences that characterize DA mature interneurons from cells in different stages of adult neurogenesis.

Pair-bonding and social experience modulate new neurons survival in adult male and female prairie voles (Microtus ochrogaster)

“…Given that dopaminergic cells process odor cues, the reduction of dopamine neurons, receptors or transporters decreases the capability to discriminate odors ( Taylor et al, 2009 ; Paß et al, 2020 ). On the other hand, calretinin interneurons are responsible for inhibiting noisy excitatory signals that reach mitral/tufted cells ( Capsoni et al, 2021 ). Interestingly, a pool of calretinin periglomerular cells remains in an immature stage for a long time, and it has been proposed that these cells could supply glomerular networks dependent on specific sensory experiences ( Benito et al, 2018 ).…”

Wide‐ranging migration and destination of early olfactory placode‐derived neurons in chick embryos

“…These cells are mature neurons with multiple processes. A GFP-labeled cell in the deep layer of the OB expressed CR, which is characteristic of the OB interneuron subtype (Capsoni et al, 2021). OB interneurons are heterogeneous and have multiple origins (Qin et al, 2017).…”

Characterization by Gene Expression Analysis of Two Groups of Dopaminergic Cells Isolated from the Mouse Olfactory Bulb

“…In particular, the outermost portion of the adult OB, termed the glomerular layer (GL), is characterized by the presence of dopaminergic (DAergic) interneurons [ 1 , 2 , 3 ]. These cells play a key role in odor processing [ 4 , 5 , 6 ]. They are responsible for significant activity-dependent plasticity, controlling the release of dopamine [ 7 , 8 , 9 , 10 ], which will lead to an adaptation of the olfactory bulbar network to external conditions.…”

“…They control the local gain of transmitter release from the terminals of the olfactory sensory neurons [ 11 , 12 , 13 ] and determine the inhibition of lateral glomerular output [ 14 ]. For a complete anatomical, functional and electrophysiological description of these neurons, the reader may refer to the reviews by Pignatelli et al [ 2 , 4 , 15 , 16 , 17 ].…”