Background: The vomeronasal organ (VNO) is specialized in detecting pheromone and heterospecific cues in the environment. Recent studies demonstrate the involvement of multiple ion channels in VNO signal transduction, including the calcium-activated chloride channels (CACCs). Opening of CACCs appears to result in activation of VNO neuron through outflow of Cl(-) ions. However, the intracellular Cl(-) concentration remains undetermined.
Results: We used the chloride ion quenching dye, MQAE, to measure the intracellular Cl(-) concentration of VNO neuron in live VNO slices. The resting Cl(-) concentration in the VNO neurons is measured at 84.73 mM. Urine activation of the VNO neurons causes a drop in Cl(-) concentration, consistent with the notion of an efflux of Cl(-) to depolarize the cells. Similar observation is made for VNO neurons from mice with deletion of the transient receptor potential canonical channel 2 (TRPC2), which have a resting Cl(-) concentrations at 81 mM.
Conclusions: The VNO neurons rest at high intracellular Cl(-) concentration, which can lead to depolarization of the cell when chloride channels open. These results also provide additional support of TRPC2-independent pathway of VNO activation.