Two predominant MUPs, OBP3 and MUP13, are male pheromones in rats.

BACKGROUND: In rats, urine-borne male pheromones comprise organic volatile compounds and major urinary proteins (MUPs). A number of volatile pheromones have been reported, but no MUP pheromones have been identified in rat urine. RESULTS: We used sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focusing electrophoresis (IEF), nano-liquid chromatography-tandem mass spectrometry (nLC-MS/MS) after in gel digestion of the proteins and quantitative real-time PCR (qRT-PCR) and showed that the levels of two MUPs, odorant-binding protein 3 (OBP3) (i.e. PGCL4) and MUP13 (i.e. PGCL1), in urine and their mRNAs in liver were higher in males than in females and were suppressed by orchidectomy and restored by testosterone treatment (T treatment). We then generated recombinant MUPs (rMUPs) and found that the sexual attractiveness of urine from castrated males to females significantly increased after the addition of either recombinant OBP3 (rOBP3) or recombinant MUP13 (rMUP13). Using c-Fos immunohistochemistry, we further examined neuronal activation in the brains of female rats after they sniffed rOBP3 or rMUP13. Both rOBP3 and rMUP13 activated the accessory olfactory bulb (AOB), medial preoptic area (MPA), bed nucleus of the stria terminalis (BST), medial amygdala (MeA), posteromedial cortical amygdala (PMCo) and ventromedial nucleus of the hypothalamus (VMH), which participate in the neural circuits responsible for pheromone-induced sexual behaviours. In particular, more c-Fos-immunopositive (c-Fos-ir) cells were observed in the posterior AOB than in the anterior AOB. CONCLUSIONS: The expression of OBP3 and MUP13 was male-biased and androgen-dependent. They attracted females and activated brain areas related to sexual behaviours in female rats, suggesting that both OBP3 and MUP13 are male pheromones in rats. Particularly, an OBP excreted into urine was exemplified to be a chemical signal.

Chronic Co-species Housing Mice and Rats Increased the Competitiveness of Male Mice.

Rats are predators of mice in nature. Nevertheless, it is a common practice to house mice and rats in a same room in some laboratories. In this study, we investigated the behavioral and physiological responsively of mice in long-term co-species housing conditions. Twenty-four male mice were randomly assigned to their original raising room (control) or a rat room (co-species-housed) for more than 6 weeks. In the open-field and light-dark box tests, the behaviors of the co-species-housed mice and controls were not different. In a 2-choice test of paired urine odors [rabbit urine (as a novel odor) vs. rat urine, cat urine (as a natural predator-scent) vs. rabbit urine, and cat urine vs. rat urine], the co-species-housed mice were more ready to investigate the rat urine odor compared with the controls and may have adapted to it. In an encounter test, the rat-room-exposed mice exhibited increased aggression levels, and their urines were more attractive to females. Correspondingly, the levels of major urinary proteins were increased in the co-species-housed mouse urine, along with some volatile pheromones. The serum testosterone levels were also enhanced in the co-species-housed mice, whereas the corticosterone levels were not different. The norepinephrine, dopamine, and 5-HT levels in the right hippocampus and striatum were not different between the 2. Our findings indicate that chronic co-species housing results in adaptation in male mice; furthermore, it appears that long-term rat-odor stimuli enhance the competitiveness of mice, which suggests that appropriate predator-odor stimuli may be important to the fitness of prey animals.

Doctoral students' academic performance: The mediating role of academic motivation, academic buoyancy, and academic self-efficacy.

Understanding influential factors for the academic performance of doctoral students is crucial for supporting their exploration of academic research opportunities and aiding their pursuit of careers in academic research. This study surveyed 659 doctoral students in China, utilizing scales to assess academic motivation, buoyancy, self-efficacy, self-concept, and performance. Based on a partial least squares structural equation modeling (PLS-SEM) analysis, a direct correlation between self-concept and performance was identified. Moreover, motivation, buoyancy, and self-efficacy were significant mediators in the relationship between self-concept and performance. To significantly enhance self-concept's impact on doctoral students' academic performance, educators should endeavor to enhance students' motivation, buoyancy, and self-efficacy. This endeavor will contribute to the discourse on academic performance and its underlying psychological mechanisms.

Tph2-/- female mice restore socio-sexual recognition through upregulating ERα and OTR genes in the amygdala.

The central 5-hydroxytryptamine system impairs sociosexual behaviors and olfaction preferences in sexually naive mice. However, it remains unknown whether reproductive experiences impart an effect on the sexual olfactory preferences of female mice lacking central serotonin. Here, we aimed at examining such effects and the underlying mechanisms using Tph2 knockout female mice. Sexually naive Tph2-/- female mice failed to recognize olfactory cues regarding sex, genetic relatedness, and social hierarchy despite exhibiting normal olfactory discrimination. However, reproduction-experienced Tph2-/- female mice recovered sexual olfactory preferences, as did sexually naive Tph2+/+ females. Meanwhile, both the estrogen receptor α and oxytocin receptor in the amygdala of reproduction-experienced Tph2-/- females presented upregulated expression at the mRNA level and an upward tendency at the protein level vs. sexually naive Tph2-/- females. Intracerebroventricular administration of a combination of estrogen receptor α and oxytocin receptor agonists, but not either agent alone, could restore the sexual olfactory preferences of sexually naive Tph2-/- female mice to some degree. We speculate that estrogen receptor α and oxytocin receptor activation in the amygdala after reproductive experiences restores sexual olfactory recognition in Tph2-/- female mice.

Correction: Tph2-/- female mice restore socio-sexual recognition through upregulating ERα and OTR genes in the amygdala.

[This corrects the article DOI: 10.1371/journal.pone.0193395.].

Author Correction: Quantitative inheritance of volatile pheromones and darcin and their interaction in olfactory preferences of female mice.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Quantitative inheritance of volatile pheromones and darcin and their interaction in olfactory preferences of female mice.

In this study, we examined how urine-borne volatile compounds (UVCs) and darcin of male mice are inherited from parents and interact to modulate the olfactory preferences of females using two inbred strains of mice, C57Bl/6 (C57) and BALB/c (BALB), and their reciprocal hybrids (BC = BALBâ™€× C57♂; CB = C57♀ × BALB♂). Chemical analysis revealed that the UVCs of C57BL/6 males were quantitatively distinguishable from those of BALB/c males. Darcin was detected in C57 urine, but not in BALB urine. The levels of UVCs and darcin in both BC and CB were intermediate between those of C57 and BALB. Behaviourally, C57 females consistently preferred BALB male urine over C57 or CB males despite that there are trace amounts of darcin in BALB urine. However, the preference for BALB urine disappeared in contact two-choice tests of BALB vs. BC pairs, and restored when recombinant darcin was added to BALB male urine. Our results suggested that both UVCs and darcin in male mice are quantitatively inherited and interact to affect the olfactory preferences of females.

Social dominance-related major urinary proteins and the regulatory mechanism in mice.

Major urinary proteins (MUPs) have been proven to be non-volatile male pheromones in mice. Here, we aimed to elucidate the relationship between MUPs and dominance hierarchy, and the underlying molecular mechanisms. Dominance-submission relationship was established by chronic dyadic encountering. We found that at the urinary protein level and hepatic mRNA level, the expression of major MUPs, including Mup20, was enhanced in dominant males compared with subordinate males, indicating that MUPs might signal the social status of male mice. Meanwhile, the mRNA level of hepatic corticotropin releasing hormone receptor 2 (CRHR2) was higher in subordinate male mice than in dominant male mice. Castration also enhanced the expression of CRHR2, but suppressed that of MUPs. CRHR2 agonist treatment reduced the expression of MUPs in liver. However, male social status failed to exert significant influence on serum testosterone and corticosterone as well as the mRNA expression of their receptors. These findings reveal that some MUPs, especially Mup20, might constitute potential dominance pheromones and could be downregulated by hepatic CRHR2, which is possibly independent of androgen or corticosterone systems.