CV responses elicited by left ventricular injection of veratrum alkaloids(VVA) in developing piglets include bradycardia, vasodilation and hypotension; the responses were abolished following bilateral vagotomy(Gootman, et al. Am. J. Phvsiol. 1986;251:H748.). However, it is unknown whether cardiac sympathetic innervation modulate these CV responses. The present study was carried out to determine whether left stellate ganglionectomy (LSG) or right stellate ganglionectomy(RSG) altered responses to left ventricular injections of VVA (20μg/kg) in pigs 3-4 wks old. Saffan-anesthetized, paralyzed open-chest piglets were artificially ventilated with 100% O2. Aortic pressure(AoP), left ventricular pressure (LVP) and ECG (Lead II) were recorded. Either RSG or LSG was carried out in each animal studied. At 30 min following RSG or LSG, a salinecontrol (0.1 ml/kg) and then the VVA injection (20 μg/kg, 0.1 ml/kg) were rapidly delivered (within 2-3 seconds) via a catheter inserted into the left ventricle. The interval between injections was 15 min. All data were recorded on a Grass Model 7C polygraph and on VCR tape for later analyses. Injections of VVA decreased (p<0.05) maximum LVP (10 ± 2 mmHg) after LSG but not after RSG. Heart rate was reduced (p<0.05) after RSG but not following LSG. Thus, the results suggest that the left stellate ganglion plays a greater role in modulating ventricular inotropy while the right stellate plays a greater role in modulating sinus rate in piglets. This study is further support of the laterality of postnatal development of cardiac sympathetic innervation (Tong, et al., Lab. Animal Sci. 1995;45:398 and Gootman et al., J. Auton. Nerv. Svst. 1992;38:191.). (Supported by NIH grant HD-28931)