Evaluation of long-term chemical sympathectomy in adult rabbits.

Administration of 6-hydroxydopamine (6-OHDA) will produce long-term sympathectomy in newborn animals. This investigation was designed to determine whether or not a long-term sympathectomy can be achieved by repeated administration of 6-OHDA in adult rabbits. Chronic treatment with 6-OHDA lowered blood pressure on average of 9 mmHg; the carotid sinus reflex was depressed, in contrast to the pressure response to intravenously administered epinephrine, which was doubled. In a constant-flow hindlimb preparation, the response to norepinephrine (NE) in 6-OHDA-treated rats was 50% larger and lasted 3 times longer. NE uptake in vitro, which is proportional to the number of adrenergic nerve endings, was found to be diminished by 80-85% in aortas from 6-OHDA-treated animals, and the dose-response curve for NE was slightly shifted to the left. The number of ganglionic cells in the superior cervical ganglia in treated animals was decreased by 80%. In conclusion, results from 6-OHDA-treated adult animals were entirely consistent with the effects of long-term sympathectomy.