Comparison of urinary odor-induced glomerular activation in the main olfactory bulb of aromatase knock-out and wild type female mice

Abstract

Previously [D.W. Wesson, M. Keller, Q. Douhard, M.J. Baum, J. Bakker, Enhanced urinary odor discrimination in female aromatase knockout mice, Horm. Behav. 49 (2006) [580][581][582][583][584][585][586] female aromatase knock out mice successfully learned to discriminate in a food-motivated go/no-go task between urinary volatiles from ovariectomized female mice treated with estradiol as opposed to estradiol plus progesterone whereas wild type females failed to learn this odor discrimination. We asked whether this behavioral difference is reflected in the ability of these two types of urinary volatiles to differentially stimulate Fos expression in juxtaglomerular cells (an index of glomerular activation) of the main olfactory bulb (MOB) in wild type versus ArKO female mice. Statistically significant differences in the profiles of MOB glomerular activation were seen in ovariectomized, estrogen-treated ArKO as well as WT female subjects following exposure to urinary volatiles from ovariectomized females given estradiol alone as opposed to estradiol plus progesterone. Therefore, previously observed differences between females of the two genotypes in their behavioral responses to these odors must reflect differential processing in more central segments of the olfactory pathway instead of in the MOB. © 2007 Elsevier Ireland Ltd. All rights reserved.Keywords: Estradiol; Progesterone; Pheromone; Sexual differentiation; Fos expression Olfactory receptor neurons in the main olfactory epithelium (MOE) that express the same olfactory receptor gene extend axons that target the same 1-2 glomeruli in the ipsilateral main olfactory bulb (MOB) [10]. Recently [6] a class of 'trace amineassociated receptors' was identified in the MOE which respond to volatile amines emitted from mouse urine. A series of studies by Restrepo and co-workers [13,12,7] showed that volatile urinary odors from male mice augmented Fos expression in juxtaglomerular cells of the MOB (an index of glomerular activation) of female conspecifics. More recently, Martel and Baum [9] used this same method to show that urinary volatiles from male versus estrous female mice activated overlapping, but distinguishable clusters of glomeruli located in the ventral portion of the MOB in both sexes. In another study [8] volatile constituents of mouse urine were shown to stimulate activity in MOB mitral cells. Wesson et al. [14] recently assessed the possible contribution of perinatal exposure to estradiol on the later ability of female mice to discriminate volatile urinary odors from * Corresponding author. conspecifics of different sexes and endocrine status. Detection of these social odorants plays a significant role in sexual, aggressive, and maternal behaviors in mice, therefore the possible role of perinatal estradiol exposure on the later ability of female mice to discriminate between urinary odors of conspecifics is of particular interest. Female mice with a null mutation of the Cyp-19 gene (ArKO mice), which encodes the estradiol synthesizing enzyme, aroma...

The main and accessory olfactory systems of female mice are activated differentially by dominant versus subordinate male urinary odors

“…This result is surprising since previous studies showed statistically significant differences in the profiles of MOB glomerular activation following exposure to different urinary odor stimuli, such as urinary volatiles from ovariectomized females given estradiol alone versus those from ovariectomized females treated with estradiol plus progesterone (Martel et al, 2007), suggesting that urinary odors vary according to the hormonal status of the female. Likewise, Schaefer and co-workers (Schaefer et al, 2001; Schaefer et al, 2002) showed that distinct clusters of MOB glomeruli were activated in female mice exposed to urinary volatiles from males carrying different haplotypes of the major histocompatibility complex.…”

Evidence for a role of early oestrogens in the central processing of sexually relevant olfactory cues in female mice

“…Fos was quantified at both the dorsal and ventral parts of the MOB as previous studies (Schaefer et al. , 2001; Martel et al. , 2007) have shown that volatile urinary odours preferentially activate the ventral MOB.…”

The main and the accessory olfactory systems interact in the control of mate recognition and sexual behavior

“…Both wild-type and ArKO females successfully learned to discriminate between other types of volatile urinary odors, including those from gonadally intact male versus ovariectomized females primed with estradiol + progesterone and those from gonadally intact versus castrated males. However, the different capacities of WT and ArKO females to discriminate volatile urinary odors from ovariectomized females treated with estradiol as opposed to oestradiol + progesterone cannot be explained by a difference between females of these two phenotypes in the ability of these two odors to activate distinguishable clusters of MOB glomeruli [70], suggesting that the central processing of social odors may be affected in female ArKO mice. In this respect, ArKO females that were treated with estradiol benzoate in adulthood to correct for their estrogen deficiency showed a normal, female-typical, Fos activation at the level of the olfactory bulbs when exposed to male urinary odors, but Fos responses were affected at more central levels [85].…”

“…without direct physical contact with the olfactory source) remains controversial but some experiments reported the activation of the AOB by volatile compounds delivered in the airstream [70,118]. In addition, other indirect behavioral evidence for a role of the VNO in the detection of volatile molecules comes from the study by Trinh and Storm [109], who used transgenic mice with a nonfunctional cAMP signaling pathway in the olfactory epithelium due to a mutation in type 3 adenylyl cyclase (AC3).…”