Artificially increasing scent mark rate increases urogenital gland size in mice Mus musculus

Estradiol's interesting life at the cell's plasma membrane

Clearly, we have presented here evidence of a very complex set of mechanisms and proteins involved with various and intricate actions of steroids at the plasma membrane. Steroids do MUCH more at the plasma membrane than simply passing passively through it. They may sit in the membrane; they are bound by numerous proteins in the membrane, including ERs, SHBG, steroid-binding globulin receptors, and perhaps elements of cellular architecture such as tubulin. It also seems likely that the membrane itself responds graphically to the presence of steroids by actually changing its shape as well, perhaps, as accumulating steroids. Clara Szego suggested in the 1980s that actions of E2 at one level would act synergistically with its actions at another level (e.g. membrane actions would complement nuclear actions). Given the sheer number of proteins involved in steroid actions, just at the membrane level, it seems unlikely that every action of a steroid on every potential protein effector will act to the same end. It seems more likely that these multiple effects and sites of effect of steroids contribute to the confusion that exists as to what actions steroids always have. For example, there is confusion with regard to synthetic agents (SERMs etc.) that have different and often opposite actions depending on which organ they act upon. A better understanding of the basic actions of steroids should aid in understanding the variability of their clinical effects.

Expression of corticosteroid binding globulin in the rat olfactory system

Glucocorticoids are known to act on the olfactory system although their mode of action is still unclear since nuclear glucocorticoid receptors are mostly absent in the olfactory mucosa. In this study we used immunocytochemistry, in situ hybridization, and RT-PCR to study the expression and distribution of corticosteroid binding globulin (CBG) in the rat olfactory system. Mucosal goblet cells could be immunostained for CBG. Nasal secretion contained measurable amounts of CBG suggesting that CBG is liberated. CBG immunoreactivity was localized in many of the basal cells of the olfactory mucosa, while mature sensory cells contained CBG only in processes as determined by double immunostaining with the olfactory marker protein OMP. This staining was most pronounced in the vomeronasal organ (VNO). The appearance of CBG in the non-sensory and sensory parts of the VNO and in nerve terminals in the accessory bulb indicated axonal transport. Portions of the periglomerular cells, the mitral cells and the tufted cells were also CBG positive. CBG encoding transcripts were confirmed by RT-PCR in homogenates of the olfactory mucosa and VNO. Olfactory CBG may be significant for uptake, accumulation and transport of glucocorticoids, including aerosolic cortisol.

Social housing influences the composition of volatile compounds in the preputial glands of male rats

In rodents the preputial glands are one of the major sources of pheromones. These volatile chemosignaling compounds are known to elicit specific behavioral and physiological effects in their conspecifics. While social stress can alter both the behavior and hormonal status of rodents, little is known about its influence on the volatile constituents of the preputial glands. We have examined the composition of volatile compounds in the preputial glands of gonadally intact male rats housed for 70 days in either unisex triads (three/cage) or singly. The rank status of triad-housed rats was based on quantitative behavioral assessments taken during the initial 30 min of triad housing. Dominant rats had heavier preputial glands compared to subdominant and subordinate rats. Capillary gas chromatography-mass spectrometry identified 56 volatile preputial compounds, of these 17 did not differ between groups while 26 compounds were significantly higher in the single-housed compared to the triad-housed rats. Six additional volatile compounds were higher in the dominant compared to the other 3 groups, while another six compounds were higher in both the dominant and single-housed rats compared to the subdominant and subordinate rats. It can be concluded that both housing condition and social rank status have significant but different effects on the composition of volatile compounds found in preputial glands of male rats. The physiological and behavioral significance of these changes in preputial gland volatile compound composition in rats remain to be investigated.

The role of chemical communication in mate choice

Chemical signals are omnipresent in sexual communication in the vast majority of living organisms. The traditional paradigm was that their main purpose in sexual behaviour was to coordinate mate and species recognition and thus pheromones were conserved in structure and function. In recent years, this view has been challenged by theoretical analyses on the evolution of pheromones and empirical reports of mate choice based on chemical signals. The ability to measure precisely the quantity and quality of chemicals emitted by single individuals has also revealed considerable individual variation in chemical composition and release rates, and there is mounting evidence that prospecting mates respond to this variation. Here, we review the evidence for pheromones as indicators of mate quality and examine the extent of their use in individual mate assessment. We begin by briefly defining the levels of mate choice--species recognition, mate recognition and mate assessment. We then explore the degree to which pheromones satisfy the key criteria necessary for their evolution and maintenance as cues in mate assessment; that is, they should exhibit variation across individuals within a sex and species; they should honestly reflect an individual's quality and thus be costly to produce and/or maintain; they should display relatively high levels of heritability. There is now substantial empirical evidence that pheromones can satisfy all these criteria and, while measurements of the actual metabolic cost of pheromone production remain to some degree lacking, trade-offs between pheromone production and various fitness-related characters such as growth rate, immunocompetence and longevity have been reported for a range of species. In the penultimate section, we outline the growing number of studies where the consequences of chemical-based mate assessment have been investigated, specifically focussing on the reported direct and genetic benefits accrued by the receiver. Finally, we highlight potential areas for future research and in particular emphasise the need for interdisciplinary research that combines exploration of chemical, physiological and behavioural processes to further our understanding of the role of chemical cues in mate assessment.

There's no place like home: cage odours and place preference in subordinate CD-1 male mice

Prior studies using mice have shown that scent marks are an important source of information and can cause behavioural changes in other individuals. Studies have also shown that scent marks in the environment can affect the outcome of social interactions between mice. We used conditioned place preference tests to investigate whether CD-1 male mice (Mus musculus) are reinforced by olfactory cues from the home cage. Soiled bedding from the home cage was presented in the initially less preferred chamber of the apparatus to determine whether this association would reduce the unconditioned preference for one chamber over the other. We tested the effects of social rank and housing condition by comparing the performance of dyads that were polarised into dominant and subordinate relationships, both when paired and when separated, with mice that were isolated throughout. The development of conditioned place preference (CPP) supported by home cage odours was influenced by social rank but not by housing condition. Only subordinate mice showed CPP to home cage odours, and this effect was seen irrespective of whether they were housed with a dominant cage mate or alone. Neither dominant (paired or separated) nor isolated mice showed any change in their preference for the chamber associated with home cage odours. This suggests that the smell of home is a more powerful reinforcer for subordinate mice in that it can produce contextual conditioning to the environment in which it is experienced.