Figure 6.

VSNs are highly selective. A, Raster plot of firing responses of one VSN to a panel of 31 sulfated steroids. The compounds were at 100 μm, except for A2534 (50 μm), E4105 (50 μm), P2135 (50 μm), C5075 (10 μm), C6905 (50 μm), and Q4765 (50 μm). Each row represents a single trial (shown grouped by stimulus, but trials to different stimuli were interleaved; 5 trials total). For this neuron, only one synthetic compound excited a reliable spiking response. The black bar represents the stimulus timing. B, Twelve single-unit response profiles to 31 sulfated steroids as in A. Normalized responses (see Materials and Methods) are shown as a color scale. The 10th neuron is shown in A. C–E, G–J, Dose/response profiles of seven single units to a set of eight structurally related compounds. Most units responded to only one of these ligands, with EC₅₀ typically in the micromolar range. The points in C marked with asterisks underestimate the real Δr because at those ligand concentrations the spike amplitude decreased during prolonged high firing rates to the point at which they could not be sorted. F, The percentage of electrodes that respond to cort21S increases as the concentration of cort21S rises. The arrow indicates the estimated concentration of cort21S in female mouse urine.