Proliferation in the vomeronasal organ of the rat during postnatal development

Abstract

We investigated proliferation of sensory cell precursors in the rat vomeronasal organ (VNO) at various postnatal ages from birth (P1) to P666. In the rat, which continues to grow during most of its adult life, proliferation might be related to growth and/or replacement. Proliferating cells were labelled by BrdU injection, and histological sections of the VNO were evaluated after immunohistochemical detection of BrdU. Proliferation density (number of proliferating cells/section) decreased dramatically from 115 at P1 to 27.2 at P21, although the area increased. Adult values were reached at P66-P333 (10.3 cells/section); at P400-P666 the value was 8.6 cells/section. Distribution of labelled cells changed considerably with age: in neonates the cells were nearly equally distributed throughout the sensory epithelium, whereas from P21 onwards most proliferating cells were concentrated in clusters near the boundaries with non-sensory epithelium. Labelled cells in the sensory neuronal layer were adjacent to the undulating basement membrane-bordering capillaries that intrude into the sensory epithelium, indicating that they were true basal cells. The volume of the sensory epithelium increased between P1 and P66, and remained constant thereafter, although the length still increased. Length and volume of the sensory epithelium were related to body size, not to sex; males and females of the same body size had the same VNO size. The complex changes in proliferation pattern during postnatal development indicate differential growth and replacement. We suggest that in adults the labelled cell clusters near the boundaries are a pool for growth, whereas proliferation in the central parts represents a replacement pool.

Distribution of olfactory epithelium in the primate nasal cavity: Are microsmia and macrosmia valid morphological concepts?

“…A similar practice has been used in recent intersex comparisons of the rodent vomeronasal organ, in which neuroepithelial measurements are scaled to body or nasal cavity size (Weiler et al, 1999;Smith et al, 2001b). However, it is known that the size of neurons does not scale isometrically with body size [see Jerison (1991) regarding similar axon diameters in mice and monkeys], and our qualitative observations on olfactory receptor cell bodies in primates of differing body mass support this.…”

The vomeronasal organ of greater bushbabies (Otolemur spp.): Species, sex, and age differences

“…Using the same sectional levels, measurements of VNNE thickness and thickness of the neuronal portion of the VNNE were measured according to the methods of Weiler et al (1999a). Briefly, the neuronal portion was measured from the basement membrane to the basal boundary of the supporting cell nuclei.…”

“…It was argued that olfactory structures simply do not scale in proportion to body size in the same manner as, for example, neural pathways related to somatosensation . However, since a number of studies have examined VNO size in the context of body size (Smith et al, 2001a;Weiler et al, 1999a), these palatal measurements taken on the sample herein were used to determine if there was sexual dimorphism of nasal cavity length.…”

“…Such differences have been reported for both absolute and/or relative (e.g., to body size) measurements (but see , for a discussion on the appropriateness for scaling data on sensory organs). A few studies have documented age-related changes in VNO size of rodents (Addison and Rademaker, 1927;Weiler et al, 1999a;Wilson and Raisman, 1980). To date, no studies have investigated such data in non-human primates.…”

Seasonal morphometry of the vomeronasal organ in the marsupial mouse, Antechinus subtropicus

“…The VNO of A. subtropicus is relatively larger than that of the adult ferret and is similar to VNO length in a juvenile (10‐day old) hamster pup weighing 10 g (Taniguchi et al, 1982). Larger rodents tend to have longer VNOs; 6 mm in the chinchilla (Oikawa et al, 1994) and 7 mm in the albino rat (Addison and Rademaker, 1927; Weiler et al, 1999b). …”