1. The pressor responses to hypertonic saline and angiotensin II introduced into the left lateral ventricle were both significantly greater in salt-sensitive (S) rats compared with salt-resistant (R) rats, with all rats on a low Na diet.
2. When S rats were given thiazide to nullify the pressor effect of dietary NaCl, their blood pressure averaged only 5 mmHg higher than that of the R rats; nevertheless, these S rats had significantly higher central nervous system pressor responses to angiotensin II and hypertonic saline.
3. Thus, if excessive dietary Na increases blood pressure by way of action on the central nervous system, these heightened pressor responses could partially account for the NaCl hypertension in S rats. Alternatively, depressed central nervous system pressor responses in R rats could partially explain the resistance of R rats to NaCl hypertension.