Olfaction and Pheromones: Uncanonical Sensory Influences and Bulbar Interactions

Abstract

The rodent main and accessory olfactory systems (AOS) are considered functionally and anatomically segregated information-processing pathways. Each system is devoted to the detection of volatile odorants and pheromones, respectively. However, a growing number of evidences supports a cooperative interaction between them. For instance, at least four non-canonical receptor families (i.e., different from olfactory and vomeronasal receptor families) have been recently discovered. These atypical receptor families are expressed in the sensory organs of the nasal cavity and furnish parallel processing-pathways that detect specific stimuli and mediate specific behaviors as well. Aside from the receptor and functional diversity of these sensory modalities, they converge into a poorly understood bulbar area at the intersection of the main- main olfactory bulb (MOB) and accessory olfactory bulb (AOB) that has been termed olfactory limbus (OL). Given the intimate association the OL with specialized glomeruli (i.e., necklace and modified glomeruli) receiving uncanonical sensory afferences and its interactions with the MOB and AOB, the possibility that OL is a site of non-olfactory and atypical vomeronasal sensory decoding is discussed.

Divergence of olfactory receptors associated with the evolution of assortative mating and reproductive isolation in mice

“…Our results indicated the highly significant enrichment of this category of receptor genes among outlier genomic regions (Figure 2B), in agreement with our functional prediction. Most Olfactory and Vomeronasal receptor outlier genes belong to OR class II and VR type 2 gene superfamilies, which can both be involved in odorant and pheromone recognition (Vargas-Barroso et al 2017). Some Olfactory Receptors, all on chromosome 9, are among the 10 most differentiated ‘top’ outlier genes ( Olfr906, Olfr907, Olfr908, Olfr914 and Olfr143 ), with Olfr906, Olfr907 and Olfr908 among the four most differentiated ones.…”

FIRST INSIGHTS IN A NON-RODENT MODEL SPECIES OF THE OLFACTORY LIMBUS. THE RED FOX (Vulpes vulpes) AS A CASE IN POINT

“…2A.2, 2B.2; 3A,B,C; 4A). The presence of these neuronal clusters in such a superficial position in the olfactory bulb is a fact, to our knowledge unpublished and surprising, because even in the case of rodents, the existing descriptions of the necklace complex (Ring et al, 1997;Luo, 2008), the atypical glomerular formations (Giannetti and Le Jeune, 1996;Gómez et al, 2005) and of the olfactory limbus itself (Vargas-Barroso et al, 2017) do not contemplate the presence of superficial clusters of neuronal somata of this nature or similar.…”

“…This area consists of a modified bulbar cortex bounded anteriorly by the dorsal MOB and posteriorly by the anterior AOB (Larriva-Sahd 2012). This area has been termed olfactory limbus (OL), and includes specialized glomeruli which receive uncanonical sensory afferences and interact with the MOB and AOB, opening the possibility that OL is a site of non-olfactory and atypical vomeronasal sensory integration (Vargas-Barroso et al, 2017).…”

Neural and Hormonal Basis of Opposite-Sex Preference by Chemosensory Signals

“…On the edge of the rostral AOB, i.e., between the dorsal part of the MOB and the AOB, there is a structure called the olfactory limbus, which receives afferents from a variety of OE receptors including TAARs. The olfactory limbus function is not yet properly characterized, but these input signals are likely aggregated to the large principal cells in the AOB and sent to the medial nucleus of the amygdala (MeA), which plays a critical role in social chemosensory signal processing [ 118 ].…”