LOCALIZATION OF DEPLETION-SENSITIVE AND DEPLETION-RESISTANT NOREPINEPHRINE STORAGE SITES IN AUTONOMIC GANGLIA

¹ Oakdale Toxicology Center, Department of Pharmacology, College of Medicine, University of Iowa, Oakdale, Iowa

The role of norepinephrine (NE) in autonomic ganglia has been difficult to assess, particularly because of incomplete knowledge of the storage sites of NE in these ganglia. This communication correlates fluorescence histochemical and electron-microscopic evidence for two morphologically distinct stores of NE in rat autonomic ganglia with very different responses to depleting drugs and to a catecholamine synthesis inhibitor. One storage site is a "chromaffin" cell, probably an interneuron, which is extremely resistant to depletion by reserpine or -methyl-m-tyrosine, and responds very slowly to -methyl-p-tyrosine. The other type of NE store is represented by clusters of small granular vesicles within the perikarya of ganglionic adrenergic neurons, in small dendrite-like processes and in nerve fibers throughout the ganglion. This latter type of NE storage site is easily depleted by reserpine and -methyl-m-tyrosine, and may be presumed to have a faster NE turnover because of the rapid response to -methyl-p-tyrosine. Because of the very different responses of these two NE stores to drugs, it would be difficult to evaluate the functional role of NE in autonomic ganglia without recourse to histochemical and fine structural studies.