Chemical sympathectomy alters the development of hypertension in miniature swine

To determine if the neurotoxin 6-hydroxydopamine could be used to chemically sympathectomize neonatal miniature swine, eight newborn swine were treated with 6-hydroxydopamine beginning on the first day after birth and continuing at regular intervals for the next 6 months. Six littermates served as controls and received vehicle injections. A significant reduction in the pressor response to intravenous tyramine (95%) and in the tissue norepinephrine content of the kidneys, left ventricle, and gastrocnemius muscle (more than 93%) provided evidence for an effective long-term sympathectomy in the 6-hydroxydopamine-treated animals. In addition, the blood pressure response of these young, chemically sympathectomized swine to chronic deoxycorticosterone acetate treatment was evaluated. Mean arterial pressure before deoxycorticosterone was similar in the 6-hydroxydopamine-treated (116±2 mm Hg) and control (125±5 mm Hg) groups. One week after deoxycorticosterone, mean arterial pressure had risen significantly by 20-22 mm Hg in both groups. Blood pressure continued to increase in the control group, reaching a value of 163±6 mm Hg by the third week after treatment. In contrast, mean arterial pressure in the 6-hydroxydopamine group did not increase further during weeks 2 and 3 after deoxycorticosterone. In conclusion, chronic treatment of neonatal swine with 6-hydroxydopamine produced an animal model with an effective, general, peripheral sympathectomy. The significant attenuation of the hypertensive response in these sympathectomized animals lends further support to the hypothesis that an intact sympathetic nervous system is necessary for the full expression of deoxycorticosterone hypertension in miniature swine.