Ciproxifan (FUB-359) is a highly effective and specific histamin H3-receptor antagonist (IC50: 9.2 nM).

H3 receptor:9.2 nM

Ciproxifan通过Ki为0.5 nM抑制[3H]HA从突触体的释放，并且通过Ki为0.7 nM抑制[125I]碘代氟比昂在大脑H3受体的结合。Ciproxifan在H3受体显示出高亲和性，但在其它受体亚型上表现出较低的表观亲和性，这是通过在孤立器官上进行的功能测试评估的（组胺H1和H2，毒蕈碱M3，肾上腺素能α1D和β1，血清素5-HT1B，5-HT2A，5-HT3和5-HT4）。[1]

PPMTase Assays : Synaptosomal membranes of rat brain cerebellum or total membranes of cultured cell lines (100,000 × g pellet) are used for methyltransferase assays in the cell-free systems. Methyltransferase assays are performed at 37°C in 50 mM Tris-HCl buffer, pH 7.4, using 100 μg of protein, 25 μM [methyl-3H]AdoMet (300,000 cpm/nmol), and 50 μM AFC (prepared as a stock solution in DMSO) in a total volume of 50 μL. DMSO concentration in all assays is 8%. Various AFC concentrations are used in several experiments as indicated in the text. Reactions are terminated after 10 min by addition of 500 μL of chloroform:methanol (1:1) with subsequent addition of 250 μL of Water, mixing, and phase separation. A 125-μL portion of the chloroform phase is dried at 40°C, and 200 μl of 1 N NaOH, 1% SDS solution is added. The methanol thus formed is counted by the vapor phase equilibrium method. Typical background counts (no AFC added) are 50-100 cpm, while typical reactions with AFC yield 500-6,000 cpm. Assays are performed in triplicate, and background counts are subtracted. Methylation of endogenous substrates and gel electrophoresis are performed. Protein carboxyl methylation in intact cells is determined using 100 μCi/mL [methyl-3H]methionine. Cells are assayed in near confluent cultures grown in 10-cm plates with 5 mL of labeling medium.