Fig. 2.

Effects of histamine (HA) receptor antagonists on HA evoked responses. Responses to agonists before and during application of modulators are in the upper and lower rows, respectively, in this figure and the next two figures. The interval between upper and lower traces in each pair is approximately 10 min. (B, D, F, and H, Insets) The summaries of the results (error bars represent SEM) of each modulator treatment, with the pretreatment amplitude served as the control. The modulator and the dose used are shown at the bottom. The voltage and time scales apply to both traces in each pair. (A and B) mepyramine (Mepy) not only blocked but reversed HA depolarization (n = 2), revealing a hidden hyperpolarization (note the difference in time courses). It attenuated HA depolarization in three others to reduce it down to 22 ± 25% (Inset). (C and D) on some neurons, cimetidine (Cime) could block or attenuate HA depolarizations down to 39 ± 24% (Inset). (E and F) On other neurons, it enhanced the depolarization to 135 ± 2%. (G and H) thioperamide (Thio) had no significant effect on HA response. Statistical significance is indicated above every histogram. ns indicates P > 0.05.