Reagent Details

Imaging information

For imaging at the H1 receptor use solutions up to 100 nM.

Pharmacological Validation

The CA200799 ligand was shown to antagonize the activity of the H1 agonist, histamine, in a recombinant CHO cell line expressing the human H1 receptor and a cyclic AMP-responsive secreted placental alkaline phosphatase (SPAP) reporter gene.

For the H₁ expressing cell line, the cyclic AMP-induced expression of SPAP was measured under basal and forskolin-stimulated (maximal) conditions. Addition of CA200799 to the basal or serum-stimulated cells did not significantly alter basal and stimulated SPAP levels, demonstrating that CA200799 has no intrinsic agonist activity.

To determine the apparent K_D for CA200799 at histamine H₁ receptors, cells were treated with varying concentrations of histamine agonist alone, or in the presence of 1µM CA200799, and the cyclic AMP-induced expression of SPAP measured.

The apparent K_D at H₁ was calculated from the rightward shift of the agonist response curve in the presence of CA200799, compared to the response curve for the agonist alone.

Similar studies were conducted with the CA200799 ligand using a recombinant CHO cell line expressing the human H₂ receptor and a cyclic AMP-responsive secreted placental alkaline phosphatase (SPAP) reporter gene. The apparent K_D at H₂ was calculated in the same way to that calculated for the human H₁ receptor.