Morphological and Immunohistochemical Features of the Vomeronasal System in Dogs

Abstract

Each of the structures integrating the sense of smell in mammals has a different degree of development, even in the so-called macrosmatic animals, according to the capacity of the olfactory system to detect thousands of different chemical signals. Such morphological diversity implies analogous physiological variation. The study of the accessory olfactory system, also known as the vomeronasal system, is a useful way to analyze the heterogeneity of the sense of smell. Macrodissection and microdissection methods as well as conventional histology and immunohistochemistry protocols were used to study aspects of the vomeronasal organ and the accessory olfactory bulbs in dogs. Observations regarding the end of the anterior part of the vomeronasal duct have been emphasized. Both lectins, Ulex europaeus agglutinin I and Lycopersicum esculentum agglutinin, and one G protein, G ai2 , show a similar pattern of binding in the sensory epithelium of the vomeronasal organ and in the vomeronasal nerve and glomerular layers of the accessory olfactory bulb, whereas the expression of protein G ao was not observed. Taken together, our results emphasize the contribution of comparative data to our understanding of the vomeronasal system function. Anat Rec, 296:146-155, 2013. V C 2012 Wiley Periodicals, Inc.

Dog and mouse: toward a balanced view of the mammalian olfactory system

“…Although numerous studies of the canine nasal mucosa have been published (Lauruschkus, 1942; Müller, 1955; Neuhaus, 1955; Adams and Hotchkiss, 1983; Kavoi et al, 2010), we are unaware of any previous systematic search for these four or five OSbS in the dog. The findings reported above, together with our previous observation that the canine vomeronasal system binds anti-G αi2 but not anti-G αo antibodies (Salazar et al, 2013), show that the dog has only the main and vomeronasal subsystems, and that the latter is in all probability entirely VR1-based.…”

“…Histologically, the VNsE is composed of basal cells, receptor neurons and supporting cells, while the anterior part of the VNO duct features stratified squamous epithelium and the posterior part simple columnar epithelium (Figure 6 and Figure S6). The immunohistochemical features of the VNsE have recently been reported elsewhere (Salazar et al, 2013) and are commented on below in the Discussion.…”

“…Whereas the murine vomeronasal system expresses the VR1-associated protein G αi2 in the apical layer of the VNsE and the anterior half of the accessory olfactory bulb (AOB), and the VR2-associated protein G αo in the basal layer of the VNsE and the posterior half of the AOB (Barrios et al, 2014), the canine system does not express G αo , and expresses G αi 2 throughout the AOB as well as in the VNsE (Salazar et al, 2013). This behavior is in keeping with reported failure to find functional VR2 genes in the canine genome (Young and Trask, 2007).…”

Morphological and histological features of the vomeronasal organ in the brown bear

“…The VNO of brown bears contained VNE, NSE, vomeronasal glands, vomeronasal cartilage and vessels like that of Asiastic black bears (Befu, 2009); histological features of the brown bear VNE are largely similar to those of dog (Salazar et al 2013). Receptor cells expressing OMP, which is known as a neuronal marker of differentiated receptor neurons of the olfactory system (Weiler & Benali, 2005), possessed both cilia and microvilli in the brown bear VNO, although these cells in mammals generally only have microvilli (Miragall et al 1979;Taniguchi & Mikami, 1985).…”

“…The VNO of rodents, marsupials and monotremes possesses both V1Rs-G ai2 and V2Rs-G ao (Jia & Halpern, 1996;Shi & Zhang, 2007;Brykczynska et al 2013). On the other hand, the vomeronasal system exclusively expresses V1Rs-G ai2 and degenerates functional V2Rs in most carnivores, ungulates and platyrrhini primates (Takigami et al 2000(Takigami et al , 2004Shi & Zhang, 2007;Young & Trask, 2007;Young et al 2010;Salazar & S anchez-Quinteiro, 2011;Hohenbrink et al 2012;Salazar et al 2013;Brykczynska et al 2013;Dinka et al 2016), whereas that of scaled reptiles exclusively possesses V2Rs-G ao and degenerates functional V1Rs (Kondoh et al 2013;Brykczynska et al 2013). The present immunohistochemical findings showed that G ai2 , but not G ao , is expressed in dendritic knobs of the vomeronasal sensory cells in the bear where receptors were located, indicating that the vomeronasal system mainly expresses V1R-G ai2 in bears as it does in other carnivores.…”