The main purpose of this study was to evaluate changes in plasma arginine vasopressin (AVP) associated with arterial baroreceptor deafferentation. Food and water intake of sham-operated (SO) rats was matched to that of sinoartic denervated (SAD) rats, and blood samples were collected from groups of SAD and SO rats 15 min, 1–4 h, 24 h and 4–7 days after operation. Plasma AVP was 2–4 times higher in SAD than SO rats at each of the times studied during the 1st week (p < 0.001); at those times no significant differences in hematocrit, plasma sodium or osmolality were found. Three weeks after surgery, plasma AVP was similar in both groups of rats. Mean arterial pressure, measured in additional groups of rats, was approximately 35 mm Hg higher in SAD than SO rats for the first 4 postsurgical hours, remaining about 20 mm Hg higher at the later times. Administration of an AVP pressor antagonist to SAD rats caused a small (8–11%), statistically significant reduction in the elevated pressure of SAD rats during the first 4 postsurgical days. Thus, AVP contributes modestly to the elevation of arterial pressure caused mainly by neurogenic mechanisms in SAD rats during the early postoperative period. Ingestive behavior was monitored in additional SO and SAD rats. SAD rats had significantly reduced food and water intake for 5 days after surgery, however, by day 6 intake was comparable to that of SO rats. Preoperative body weight was not regained until 2 weeks after surgery. The results indicate that sinoaortic baroreceptor reflex pathways interact with systems regulating AVP secretion and ingestive-metabolic processes as well as with those autonomic systems directly affecting cardiovascular f