抄録
We have developed the coculture system of the vomeronasal organ (VNO), which detects the pheromonal chemosignals, and the accessory olfactory bulb (AOB), the first relay station of the vomeronasal system, to investigate the regulatory mechanisms for vomeronasal development. The rat vomeronasal neurons can not mature in the singly cultured VNO, but morphologically show the maturational characteristics in the coculture with the AOB. To investigate whether morphological changes are accompanied by functional maturation, we applied charged compounds in urine iontophoretically into the cultured VNO using a microelectrode and analyzed responses by a Ca2+ imaging method with or without cultured AOB neurons. The rat VNO cocultured with the AOB neurons could respond to rat urine, which was ejected into the cocultured VNO with a negative current. These VNO responses were not observed without AOB neurons, by urine-ejection with a positive current or by the ejection of artificial urine. Interestingly, the cocultured VNO could respond to not only rat but also mouse urine. Moreover, all of a western blot, a RT-PCR and an immunofluorescence analyses clearly indicated that the expression of two representatives (VR1 and VR4) from different subfamilies of the V2R family of vomeronasal receptors was significantly enhanced in co-culture. These results indicate that vomeronasal neurons result in expressing vomeronasal receptors by interacting with AOB neurons in co-culture, and then acquiring responsiveness to negatively charged compounds in urine. [J Physiol Sci. 2008;58 Suppl:S169]
