Fig. 6. Effects of HAergic antagonists on the HA evoked-current in X-organ neurons. (A–D) Current traces evoked by HA (5 µmol l^–1, 10 s) after, during and before the superfusion of H1 and H2 antagonists at the indicated concentrations; all the records were obtained at a holding potential of –40 mV, and the interval between pulses was 3 min. Note that in all cases the blockage was reversible. (E) Normalized peak currents (mean ± s.e.m.) versus log molar concentration of H1 and H2 antagonists (4–6 observations per point; see the IC₅₀ values in the text). Squares, tiotidine; diamonds, cimetidine; circles, ranitidine; triangles, mepyramine.