Physiological investigation of sensory signaling mechanisms in the mouse accessory olfactory system

One of the great success stories of evolution is conspecific social communication. In most mammalian species, olfactory cues from bodily fluids serve to communicate the current constitution of individuals. The accessory olfactory system (AOS) is dedicated to detect such social cues, a process that plays a central role in regulating essential behaviors. Despite its importance, many of the fundamental AOS functions remain elusive. Therefore, the overall aim of this thesis was to deepen our understanding about signal detection mechanisms and the overall function of the vomeronasal organ (VNO). I first revisited the concept of non-adapting vomeronasal sensory neurons (VSNs). Together with the groups of Prof. Dr. Julian Meeks and Prof. Dr. Anna Menini, I showed that short-term adaptation emerges in VSNs in the time frame of tens of seconds upon repetitive exposure to natural stimuli. Such adaptation was also revisable in the course of minutes. In addition, investigation of sex-dependent urine responses revealed adaptation to same-sex, but not to opposite-sex urine at intermediate inter-stimulus intervals. This result suggests that VSN sensory adaptation is modulated by sensory experience. My findings thus establish VSN sensory adaptation and form the basis for future studies on this phenomenon. As part of a collaboration with colleagues Prof. Dr. Yoram Ben-Shaul and Prof. Dr. Pavel Stopka, I investigated the extent to which secretions from inbred laboratory mice and wild conspecifics differ. I collected data from 25,332 VSNs that reveal the potential of VSNs to distinguish between strain-specific signals from wild mice of different origin as well as from C57BL6/j and BALB/c mice. Despite reports of a much more complex chemical signature, signals induced by wild urine were not more prominent. However, these results emphasize the importance of the VNO in interspecific communication. Interestingly, I determined different VSN response profiles for male and female and for C57BL6/j and BALB/c mice. This result suggests expression of different vomeronasal receptor repertoires in male and female mice, as well as in different inbred laboratory strains. Altogether, the results in this thesis, some of which have been published (Wong et al., 2018), provide new and important insights into VNO function