Paraganglia of the rat recurrent laryngeal nerve after long-term hypoxia: a morphometric and biochemical study.

Paraganglia of the recurrent laryngeal nerve of rats exposed to hypoxia (10 +/- 0.5% O2) for 3 weeks became enlarged in volume by 2.6-fold. The volume densities of blood vessel lumen and endothelial cells were unchanged. The enlargement of the paraganglia was mainly attributed to hypertrophy of the dense-cored vesicle-containing cell. Concerning the profile diameter of the vesicle, a unimodal distribution of dense-cored vesicle cells was found in both control and hypoxic paraganglia. The vesicle diameter increased by about 19%, whereas the numerical density of dense-cored vesicles and the vesicle volume density were unaltered after hypoxia. Recurrent laryngeal nerves assayed by a sensitive high performance liquid chromatography technique contained an average of 1.9 pmol dopamine and 1.3 pmol norepinephrine. Exposure to 2 weeks of hypoxia increased the dopamine level to 4.9 pmol, whereas the norepinephrine content was unchanged. It is suggested from this study that the catecholamines determined are housed in the paraganglia of the recurrent laryngeal nerve.