The effect of 6-hydroxydopamine on nerves in the rat upper urinary tract

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Abstract
The effect of a single large dose of 6-hydroxydopamine (6-OHDA) on adrenergic nerves in the rat upper urinary tract has been investigated by both light and electron microscopy. Reduction in the intensity of fluorescent catecholamine-containing nerves was seen 1–2 h after drug treatment. At 3–5 h, fluorescing nerves were absent from all preparations. Forty-eight hours after injection fine catecholamine-containing nerves could not be detected, although a few large nerves adjacent to vessels and in the adventitia of the upper urinary tract were associated with increased fluorescence. Using the electron microscope, axons related to smooth muscle were seen to be swollen and contained aggregations of small (50 nm diameter) granulated vesicles and electron-dense material 3–6 h after drug treatment. Other axons contained damaged mitochondria and were devoid of neurofilaments and neurotubules. Normal axons were also seen, some of which contained accumulations of small (50 nm diameter) agranular vesicles and occasional large (100 nm diameter) granulated vesicles. In the submucosa, damaged axons were observed lying close to, or occasionally running between, basal epithelial cells. Axons containing electron-dense clumps of synaptic vesicles were not observed in this situation. Normal axons containing accumulations of small agranular vesicles were identified, some of which were closely related to damaged axon profiles. Forty-eight hours after the drug treatment, some axons related to smooth muscle cells contained accumulations of electron-dense material. All other axons in the wall of the upper urinary tract appeared normal. These results are discussed in relation to the distribution of various types of autonomic nerve in the upper urinary tract.