FIGURE 4.

A, both CysNO and H₂O₂ rapidly lowered the perfusion pressure in rat coronary vessels, with the former exerting a more marked vasodilatory response. B, isoprenaline rapidly reduced coronary perfusion pressure. When SNAP was then administered simultaneously with isoprenaline (ISO), perfusion pressure remained depressed and similar to that observed with isoprenaline alone. This lack of effect of SNAP on perfusion pressure was in marked contrast to its negative influence on LVDP (Fig. 3C). C, aerobically perfused isolated hearts exposed to the PKG inhibitor KT5823 responded with a marginal time-dependent increase in perfusion pressure, which may be consistent with a limited contribution of this kinase to coronary tone under basal conditions. D, during the treatment of the aerobic heart with the KT5823 inhibitor, there was a small time-dependent depression in LVDP contractility.