Abstract: AIM: To investigate the electrophysiological effects of extrinsic autonomic nerves on the atrium by stimulating rabbit cervical vagosympathetic trunk (CVST) using different electrical intensities. METHODS: Ten New Zealand rabbits were anesthetized. A 6F electrical catheter was inserted into the right cardiac atrium through right jugular vein. The atrial effective refractory period (AERP), P-wave dispersion (PD), the number of rabbits with atrial fibrillation (AF) and the window of atrial vulnerability (WOV) were measured and recorded by programmed electrical stimulation (PES). Bilateral CVSTs were then disassociated, exposed and stimulated by different intensities to reduce the heart rate (HR) by 10%, 30% and 50%, respectively. The same PES was given and the same indexes were recorded. RESULTS: Compared with the baseline, the shortening of AERP was significant (P<0.05) when the intensity of stimulating left CVST was increased to reduce the heart rate by 50% or that of stimulating right CVST was increased to reduce the HR by 30%, or that of bilateral CVST was increased to reduce the HR by 10%. A significant change in PD was also observed (P<0.05) when the intensity of stimulating left CVST was increased to reduce the HR by 50% or that of stimulating right and bilateral CVST to reduce the HR by 30%. More remarkable changes were observed with the increasing stimulating intensity (P<0.01). However, no significant difference was observed in the number of rabbits with AF between stimulating right, left or bilateral CVST or between different stimulating intensities. Only when the intensity of stimulating bilateral CVSTs was increased to reduce the HR by 50%, the widening of WOV was significant ［from (3.4±1.5) msec to (7.6±3.5) msec; P<0.05］. CONCLUSION: Electrophysiological characteristics of the right atrium are influenced by bilateral CVSTs where the effect of right CVST is predominant. There is a coordinating effect of both CVSTs on the electrophysiologic characteristics of the right atrium.