Effects of 5-hydroxydopamine and 6-hydroxydopamine on the ultrastructure of type I cells in paraganglia of the rat recurrent laryngeal nerve.

The ultrastructure of the Type I cells in paraganglia of rat recurrent laryngeal nerve (RLN) was studied after the administration of 5-hydroxydopamine (5-OHDA) and 6-hydroxydopamine (6-OHDA). Normal Type I cells of RLN-paraganglia contained abundant organelles and their cytoplasm was characterized by the presence of numerous membrane-bounded dense-cored vesicles (DCVs). The DCVs were round in profile (diameter 107.67 +/- 0.06 nm, all values expressed as mean +/- s.e.m. in the present study) and possessed dense cores of moderate to low electron density. After 5-OHDA treatment (single injection, 100 mg/kg b.w., i.v.), the majority of DCVs were filled with a material of high electron density. No significant difference was observed between the profile diameter of the DCVs in 5-OHDA-treated rats (104.96 +/- 0.06 nm) and that in normal rats. After 6-OHDA treatment (three injections, 100 mg/kg b.w. each at 12 h intervals i.p.), no significant alteration in the electron density of the core was noted. However, most of the DCVs were enlarged and round, elliptical or irregular in profile (190.57 +/- 2.77 nm x 130.34 +/- 2.09 nm). The dense core of DCVs was centrally or eccentrically located in DCVs. The results of the present study indicate that: 1) there is only one type of granulated glomus cell (i.e., Type I cells) in the rat RLN-paraganglia under normal physiological condition; and 2) since the ultrastructural morphology of DCVs in Type I cells of rat RLN-paraganglia is altered after 5-OHDA or 6-OHDA treatment, these cells may possess mechanisms for the uptake of false adrenergic neurotransmitter and/or neurotoxin.