Figure 1.

Effects of tramadol on catecholamine (CA) secretion induced by carbachol (A), veratridine (B) or high K⁺ (C) in bovine adrenal chromaffin cells. Cells were incubated with carbachol (300 μM), veratridine (0.1 mM) or a high K⁺ (56 mM) solution in the presence of various concentrations of tramadol for 5 min at 37°C. Catecholamine secreted into the medium were measured (see Methods), and expressed as percentage of total catecholamines. Data are means±s.e.mean of four experiments. *P<0.05, **P<0.01 compared with carbachol alone.