Fig. 3.

Effects of antagonists for H1, H2, and H3 subtypes on responses evoked by respective agonists. (A and B) mepyramine (Mepy) was able to block BH depolarization to 5 ± 10% of pretreatment amplitude. (C and D) depolarization by DI (dimaprit) occurred only in one unit, with an average amplitude of 9 mV over three stimulations. It was reversed 3 min after cimetidine (Cime) perfusion into a hyperpolarization. During washout, the hyperpolarization was reduced to zero and the depolarization recovered to 3 mV. (E and F) when DI caused hyperpolarizations, cimetidine enhanced the amplitude to 140 ± 36%. (G and H) thioperamide (Thio) had a tendency to enhance the hyperpolarizations caused by IM (imetit).