Figure 1.

Effect of histamine (HA) on forskolin (FSK)-induced cAMP accumulation in CHO cells expressing various densities of the rH₃₍₄₄₅₎ and rH₃₍₄₁₃₎ receptor isoforms. cAMP accumulation was induced by forskolin (3 µM) alone or in the presence of histamine (1 µM) in CHO(rH₃₍₄₄₅₎R) and CHO(rH₃₍₄₁₃₎R) cells expressing increasing isoform densities (up to 1000 fmol·mg⁻¹ protein, as determined using [¹²⁵I]IPX binding assay). The results are means ± SEM of values from two to six different experiments with five determinations each. *P < 0.01, **P < 0.001, significantly different from forskolin alone.