Airborne molecules released from male mouse urine affect female exploratory behavior

Abstract

Male mouse urine delivers a wide range of molecules which may be involved in intraspecific chemical communication. These include the Major Urinary Proteins (MUP) which bind volatile odorant molecules and slowly release them from urine marks. The aim of this work is to evaluate the role of volatile molecules in eliciting exploratory behavior, in comparison to MUP. Female mice were exposed to male mouse urine, either diluted or not, or to MUP stripped of ligands. Gas chromatography and mass spectrometry of the stimuli were performed to verify the presence and identify the odorant molecules in urine and to assess the absence of MUP ligands. The exploratory behavior of adult female mice was analyzed in a cage, in the presence of two stimuli on opposite sides, but preventing direct contact with them. Four stimuli were presented in pairs: adult male mouse urine, MUP stripped of ligands, urine diluted 100 times and water as control. The results show that adult female mice explore urine, as little as 150 nl, but do not explore MUP stripped of ligands. These data show that male urine airborne molecules, effective at very low doses, mediate initial stimulus exploration by female mice.

Regulation of volatile and non-volatile pheromone attractants depends upon male social status

“…We compared the following stimuli in our olfactory discrimination experiments: (1) adult male urine versus water (‘positive control’ to confirm that females in our assay are attracted to the scent of male urine 61 ; N = 15 subjects in estrus; pooled male urine); (2) adult male versus adult female urine (‘sex discrimination’; N = 10 subjects in estrus; pooled urine of same-sex individuals); (3) dominant males versus subordinates (‘social status discrimination’; N = 10 subjects tested during the estrous and diestrous phases; male urine from enclosure treatment); and (4) high versus low urinary protein concentration (‘concentration discrimination’; N = 10 subjects in estrus; urine from the same male donor (N = 10) collected on two different days; 3:1 high:low PC ratio, see below).…”

“…Longitudinal studies are needed to examine pheromone excretion in social interactions and with controls for comparison. Finally, the regulation of MUPs and volatiles have mainly been investigated independently, with few exceptions 61 and studies are needed to examine how MUP regulation influences odor, as well as the excretion of volatiles.…”

Proteins and peptides as pheromone signals and chemical signatures

“…Dominant males produce large quantities of this MUP in their urine, which they use to mark their territory (Hurst & Beynon, 2013;Roberts, Davidson, Beynon, & Hurst, 2014). Volatiles in the urine marks attract female mice (Redaelli, Orsetti, Zagotto, Cavaggioni, & Mucignat, 2014;Roberts et al, 2014). As their nostrils touch the urine marks, molecules of darcin are sniffed into the VNO, which pumps them into the sensory zone of the VNO.…”

Effects of point mutations in the binding pocket of the mouse major urinary protein MUP20 on ligand affinity and specificity

“…molecular size, chemical structure, hydrophilic/hydrophobic balance, and hydrogen bonding properties (Table 1). In particular, 2-isobutyl-3-methoxypyrazine (PYR) is a low-threshold odor 30,31 , used in MUPs/ligand binding studies 4,7 , methylnapthalene-1,4-dione (menadione, MEN), a naphtoquinone analogue of vitamin K is also found in MUP scent marks 32 while 2,4-dimethylphenol (2,4-DMP), and 2-butyl-1-octanol (OCT), along with linalool (3,7-dimethylocta-1,6-dien-3-ol) (LIN), contribute to urine scent marks in male mice 9,33 . L-Adrenaline (L-ADR) was also tested as a precursor of vanilloid ligands, which may bind to Transient Receptor Potential Vanilloid (TRPV) receptors widely found in the olfactory epithelium 34 .…”