It has been suggested in anesthetized animals that the occurrence of sequences of consecutive beats characterized by systolic arterial pressure (SAP) and RR or pulse (PI) interval changing in the opposite direction (SAP+/RR- and SAP-/RR+, nonbaroreflex sequences) might represent the expression of neural cardiovascular regulatory mechanisms operating with feedforward characteristics. Aim of the present study was to study nonbaroreflex sequences in a more physiological experimental model, i.e. conscious freely moving rats. We studied conscious rats before and after: 1) complete autonomic blockade (n=12; CAB); 2) sympathetic blockade (n=10; SB); 3) (n=7) and (n=8) adrenergic blockade; 4) parasympathetic blockade (n=10; A). Nonbaroreflex sequences were defined as 3 or more beats in which SAP and PI of the following beat changed in the opposite direction. CAB reduced the number of nonbaroreflex sequences (95.6 ± 9.0 vs 45.2 ± 4.1, P<0.001), as did SB (80.9 ± 12.6 vs 30.9 ± 6.1, P<0.001). Selective receptors blockade did not induce significant changes (80.9 ± 12.5 in baseline vs 79.0 ± 14.7 after prazosin) whereas receptors blockade reduced significantly nonbaroreflex sequences occurrence (80.9 ± 12.5 in baseline vs 48.9 ± 15.3 after propranolol). A produced a significant increase of nonbaroreflex sequences (95.1 ± 6.9 vs 136.0 ± 12.4, P<0.01). These results demonstrate the physiological role of nonbaroreflex sequences as expression of feedforward type of short-term cardiovascular regulation able to interact dynamically with the feedback mechanisms of baroreflex origin in the neural control of sinus node.