We designed this experiment to evaluate effects of intravenous bolus injection of air (0.5 ml.kg-1) on systemic blood pressure (SBP), central venous pressure (CVP), and renal nerve activity (RNA) in urethane-anesthetized rabbits. Animals were divided into the following three groups: animals with neuraxis intact (I group, N = 5), cervical vagotomized animals (V group, N = 5) and sinoaortic denervated animals (SAD group, N = 4). All animals were placed on the right-side down position to avoid effects of the posture throughout the experiments of air embolism. In the I group, air caused profound hypotension (from 95 +/- 10 to 54 +/- 15 mmHg) associated with a significant increase in CVP (from 2 +/- 2 to 7 +/- 3 mmHg) twenty seconds after the injection of air. In spite of the significant hypotension, RNA response did not show any increase for twenty seconds. This response was followed by an augmentation in RNA thirty seconds after air injection. In contrast, vagotomized animals exhibited a significant RNA increase (147 +/- 11% of the control) in response to a decrease in SBP (from 93 +/- 6 to 78 +/- 5 mmHg) and an increase in CVP ten seconds after the administration of air. In SAD group, a rapid and remarkable decline in SBP (from 85 +/- 13 to 47 +/- 12 mmHg) occurred ten seconds after the injection of air. Despite this hypotension, RNA decreased nearly to a noise level after administration of air.(ABSTRACT TRUNCATED AT 250 WORDS)