Fig. 5. Production of Ins(1,4,5)P₃ after exposure to urine from castrated males. C57BL/6 female vomeronasal organ (VNO) microvillar membranes responded to whole urine and urine from BALB/c castrated males with an increase in the production of Ins(1,4,5)P₃ (*P<0.05). The addition of H-2^d peptide further increased the production of Ins(1,4,5)P₃, though not significantly. Reactions were performed without stimulus, in the presence of whole urine, urine from castrated males, and urine from castrated males supplemented with MHC peptide. Values are means ± s.e.m. of at least five independent experiments, each consisting of duplicate measurements.