Activation of the renin-angiotensin system in the brain is considered important in the arousal and expression of sodium appetite. To clarify the effects of directly activating this hormonal cascade, taste neurons in the nucleus of the solitary tract of rats were tested with a battery of sapid stimuli after intracerebroventricular injection of renin or its vehicle. The rats were chronically prepared, but lightly anesthetized during the recording procedure. Eighty-five taste neurons were tested; 46 after renin injections, 39 after vehicle. Neural activity was counted for 5.0 s periods without stimulation (spontaneous), and during stimulation with water and sapid chemicals. The averaged responses to each of the standard stimuli (0.1 M NaCl, 0.3 M sucrose, 0.01 M citric acid, and 0.01 M quinine hydrochloride) did not differ significantly between the 2 conditions. When the rats were tested with a concentration range of NaCl, however, the average responses to the hypertonic 0.3 M and 1.0 M stimuli after renin were reduced to 74% and 70%, respectively, compared with those after vehicle injections. A similar tendency was evident for the subsample of neurons that responded best to NaCl, but the effect was smaller. These data are consistent with, but not as dramatic as, those reported after dietary-induced sodium appetite.