| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2004: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Pheromones are detected by unique receptors in the vomeronasal organ (VNO), and then affect endocrinal status and behavior in various kinds of animals. Although it is well known that the VNO mediates sexually and developmentally different behavioral and neuroendocrine responses, the cellular mechanisms regulating these functions are not, much understood. The differences in pheromonal effects might be in part due to differential expression of pheromone receptors. In this project, I established the co-culture system of vomeronasal receptor neurons (VRN) and accessory olfactory bulb (AOB) neurons to assess roles of each neuronal species in the vomeronasal system on the pheromonal signal processing. Firstly, I demonstrated the synapse formation between cultured VRNs and AOB neurons using a calcium imaging technique combined with electrical stimulation and analyzing pharmacologically. Secondly, it was showed that the maturation of VRNs was induced by co-culture with dissociated AOB neurons.
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To characterize the receptor expression, I examined two representatives (VR1 and VR4) from different subfamilies of the V2R family of pheromone receptors in cultured VRNs. A western blotting analysis showed the expression of VR1 and VR4 in VRNs was induced and increased with days in co-culture, an effect which was not observed in the VRN-alone culture. Moreover, we applied charged compounds in mouse urine iontophoretically to the VRNs using a microelectrode and analyzed VRN response by a Ca^<2+> imaging method with or without cultured AOB cells. When urine compounds were ejected to the VRNs co-cultured with AOB cells with a current of -2μA, subpopulation of VRNs clearly showed long-lasting Ca^<2+> increases. Injections of a current below -5μA alone had no effect to the VRNs. Such Ca^<2+> increases were not observed without AOB cells. These results indicate that VRNs result in expressing pheromone receptors by interacting with AOB neurons, and then acquiring responsiveness to compounds in urine. Less
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