To observe the effect of beta(3)-adrenoceptor (AR) in regulating resting intracellular Ca(2+) concentration of the ventricular myocytes and investigate the signaling pathway in rats with experimental heart failure.Rat models of experimental heart failure were established by ligation of the anterior descending artery, and the myocytes were isolated by enzymatic digestion. The resting intracellular Ca(2+) concentration was determined using laser scanning confocal microscopy (LSCM) in the cells stimulated with 1 micromol/L BRL37344 (a selective beta(3)-AR agonist) alone or in combination with PTX, L-NAME, or methylene blue.In the ventricular myocytes from normal control rats, BRL373444 reduced the resting intracellular Ca(2+) concentration of by 45.5%, while the reduction increased to 59.4% in the cells from rats with heart failure. In combination with L-NAME (10 micromol/L), methylene blue (10 micromol/L), and PTX (2 microg/ml), BRL373444 caused a reduction in resting intracellular Ca(2+) concentration of the ventricle myocytes from normal control rats by 10.1%, 16.9%, and 15.4%, respectively in control group, while the rate was 16.9%, 19.3%, and 11.7% in the heart failure group.Beta(3)-AR agonist can decrease the resting intracellular Ca(2+) concentration of the ventricular myocytes, but the reduction is smaller in cells from rats with heart failure than in cells of normal rats. This effect is mediated through the PTX-NOS-NO pathway.