Fig. 4. X-organ neuron sensitivity to HA. (A) Representative HA-evoked currents obtained at –40 mV holding potential, during application of HA pulses at the indicated concentrations. (B) Peak currents (mean ± s.e.m.) versus HA concentration (3–5 observations per point). The solid line correspond to a non-linear regression using I_max=1/[1+(EC₅₀/HA)ⁿ], where HA=molar HA concentration, n=the Hill coefficient and EC₅₀=HA concentration giving half-maximal effect, being the free parameters. The fit yielded EC₅₀=3.3±1 µmol l^–1 and n=2.6±0.4.