Pathophysiological implications of the vascular nitric oxide (NO)/cGMP pathway were investigated in various rat models of hypertension. The expression of brain and endothelial constitutive NO synthases (bNOS, ecNOS) was determined by Western blot analysis, and the biochemical activity of soluble and particulate guanylate cyclases (GC) was assessed by the amount of cGMP generated in the thoracic aortae of rats with deoxycorticosterone acetate (DOCA)-salt, two-kidney, one dip (2K1C), and spontaneous hypertension (SHR). Plasma nitrite/ nitrate levels were decreased in DOCA-salt and 2K1C hypertension, and increased in SHR. The vascular expression of bNOS as well as that of ecNOS was decreased along with tissue nitrite/nitrate contents in DOCA-salt and 2K1C hypertension. The expression of both bNOS and ecNOS was increased in SHR with concomitant changes of tissue nitrite/nitrate contents. The activity of soluble GC was decreased, and that of particulate GC was increased in DOCA-salt hypertension. The soluble GC activity was increased, while the particulate GC activity was not affected in 2K1C hypertension. The soluble GC activity was not significantly changed, but the particulate GC activity was decreased in SHR. These results indicate that the high blood pressure is associated with differentially-altered vascular NO/cGMP pathway in different models of hypertension.