Responses to sulfated steroids of female mouse vomeronasal sensory neurons.

The rodent vomeronasal organ plays an important role in many social behaviors. Using the calcium imaging technique with the dye fluo-4 we measured intracellular calcium concentration changes induced by the application of sulfated steroids to neurons isolated from the vomeronasal organ of female mice. We found that a mix of 10 sulfated steroids from the androgen, estrogen, pregnanolone, and glucocorticoid families induced a calcium response in 71% of neurons. Moreover, 31% of the neurons responded to a mix composed of 3 glucocorticoid-derived compounds, and 28% responded to a mix composed of 3 pregnanolone-derived compounds. Immunohistochemistry showed that neurons responding to sulfated steroids expressed phosphodiesterase 4A, a marker specific for apical neurons expressing V1R receptors. None of the neuron that responded to 1 mix responded also to the other, indicating a specificity of the responses. Some neurons responded to more than 1 individual component of the glucocorticoid-derived mix tested at high concentration, suggesting that these neurons are broadly tuned, although they still displayed strong specificity, remaining unresponsive to high concentrations of the ineffective compounds.