The von Bezold-Jarisch reflex (BJR) is a vagally-mediated chemoreflex from the heart and lungs, causing hypopnea, bradycardia and inhibition of sympathetic vasomotor tone. Cardiac sympathetic nerve activity (CSNA) has not been systematically compared with vasomotor activity during the BJR, however. In 11 urethan-anesthetized (1-1.5g/kg, i.v.), artificially ventilated rats we measured CSNA simultaneously with lumbar sympathetic activity (LSNA) while the BJR was evoked by right atrial bolus injections of phenylbiguanide (PBG; 0.5, 1.0, 1.5 and 2µg). Nerve and heartbeat responses were analyzed by calculating normalized cumulative sums (CUSUMs). LSNA and heartbeats were always reduced by the BJR. An excitatory 'rebound' component often followed the inhibition of LSNA, but never outweighed it. For CSNA, however, excitation usually (in 7/11 rats) outweighed any initial inhibition, such that the net response to PBG was excitatory. The differences in net response between LSNA, CSNA and heartbeats were all significant (P 0.01). A second experimental series on 7 rats showed that methyl atropine (1mg/kg i.v.) abolished the bradycardia of the BJR, while subsequent bilateral vagotomy substantially reduced LSNA and CSNA responses, both excitatory and inhibitory. These findings show that during the BJR: 1) CSNA is often excited; 2) there may be co-activation of sympathetic and parasympathetic drives to the heart; 3) divergent responses may be evoked simultaneously in cardiac vagal, cardiac sympathetic and vasomotor nervous pathways; 4) those divergent responses are mediated primarily by the vagi.