Assessing Sympathetic Function from Dynamics of Norepinephrine Metabolism and False Transmitters
About 40 years ago, tritiated norepinephrine (3H-NE) and epinephrine (3H-EPI) were introduced as a means for examining the fate of catecholamines in experimental animals and in humans. By examining the urinary products of 3H-EPI and 14C-metanephrine, the O-methylated product of EPI, it was shown that O-methylation of the administered catecholamine was the major means of metabolic termination of its action.1 When 3H-NE was administered, a major portion of the administered radioactivity appeared to be sequestered in the tissues, such as the hearT., that were richly innervated by sympathetic nerves.2 After chronic denervation, however, this uptake of 3H-NE was abolished, indicating that intravenously administered catecholamines are taken up into sympathetic nerve terminals.3 The supersensitivity to NE released from sympathetic nerves that developed after such denervation indicated that reuptake was the major means of terminating the action of released NE.
KeywordsSympathetic Nerve Autonomic Failure Sympathetic Function Sympathetic Nerve Terminal Cardiac Sympathetic Denervation
Unable to display preview. Download preview PDF.
- 2.Whitby, L.G, Axelrod J., and Weil-Malherbe, H.: The fate of 3H-norepinephrine in animals J. Pharmacology 132: 193–201,1961Google Scholar
- 9.Kopin ü, Rundqvist B., Friberg P., Lenders J, Goldstein DS, Eisenhofer G. Different relationships of spillover to release of norepinephrine in human hearT., kidneys, and forearm. Am J Physiol. 275 :R 165–73, 1998.Google Scholar
- 11.Eisenhofer G, Hovevey-Sion D., Kopin IJ, Miletich R, Kirk KL, Finn R, Goldstein DS. Neuronal uptake and metabolism of 2- and 6-fluorodopamine: false neurotransmitters for positron emission tomographic imaging of sympathetically innervated tissues. J Pharmacol Exp Ther. 1989 Jan;248:419–427.PubMedGoogle Scholar