Distinct Signals Conveyed by Pheromone Concentrations to the Mouse Vomeronasal Organ

Abstract

In mammalian species, detection of pheromone cues by the vomeronasal organ (VNO) at different concentrations can elicit distinct behavioral responses and endocrine changes. It is not well understood how concentration-dependent activation of the VNO impacts innate behaviors. In this study, we find that, when mice investigate the urogenital areas of a conspecific animal, the urinary pheromones can reach the VNO at a concentration of ϳ1% of that in urine. At this level, urinary pheromones elicit responses from a subset of cells that are tuned to sex-specific cues and provide unambiguous identification of the sex and strain of animals. In contrast, low concentrations of urine do not activate these cells. Strikingly, we find a population of neurons that is only activated by low concentrations of urine. The properties of these neurons are not found in neurons responding to putative single-compound pheromones. Additional analyses show that these neurons are masked by high-concentration pheromones. Thus, an antagonistic interaction in natural pheromones results in the activation of distinct populations of cells at different concentrations. The differential activation is likely to trigger different downstream circuitry and underlies the concentration-dependent pheromone perception.

Chemosensory burst coding by mouse vomeronasal sensory neurons

“…1, A-C). As has previously been reported (Nodari et al 2008;Meeks et al 2010;He et al 2010;Arnson and Holy, unpublished observations), VSNs increased their firing rate in response to sulfated steroids with a monotonic dependence on concentration (Fig. 1D).…”

“…The murine accessory olfactory system has been subject to a number of recent studies spanning both sensory neurons and downstream circuits (Meeks et al 2010;Ben-Shaul et al 2010;Hendrickson et al 2008;He et al 2008He et al , 2010Nodari et al 2008); however, the question of how information is being represented at the level of individual spikes has not been explored. In this study, we aimed to elucidate the physiological properties of VSNs that relate to how stimulus information is encoded and to explore the implications of these properties for decoding sensory responses.…”

Roles of sex and gonadal steroids in mammalian pheromonal communication

“…Unfortunately, no manipulations of females' sex hormone status were carried out, and male VNO slices were not studied. More recently, He et al (2008He et al ( , 2010) studied the ability of male vs. female urinary odors to elevate intracellular calcium (an index of VNO receptor Fig. 3.…”

Calcium Imaging of Vomeronasal Organ Response Using Slice Preparations from Transgenic Mice Expressing G-CaMP2

“…We have developed transgenic mice that express G-CaMP2 in the olfactory sensory neurons, including the VSNs (15, 25). The sensitivity and the genetic nature of the probe greatly facilitate Ca 2+ imaging experiments by eliminating the dye loading process (4, 20).…”