ISSN:
1432-0878
Keywords:
Axonal migration
;
Catecholamines
;
Sciatic nerve
;
Radioautography
;
Electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The radioautographic technique has been used to study the axonal migration of catecholamines in sympathetic fibres of the sciatic nerve of rats after ligature. A first series of experiments aimed at ascertaining the capacity of the proximal portion of adrenergic fibres to take up and store exogenous tritiated catecholamines (3H-DOPA; 3H-DA and 3H-NA) 3 to 22 hours after ligation. The results are qualitatively similar in rats pretreated and non-pretreated with IMAO, but the intensity of the radioautographic reaction is lower in the latter cases. Most of the labeled axons are filled mainly with vesicular and tubular profiles of endoplasmic reticular origin, large dense bodies (probably lysosomes) and/or mitochondria. The silver grains are generally superimposed on the vesicular and/or the tubular profiles, but in some cases on the large dense bodies, suggesting that exogenous catecholamines can be stored in lysosomes. The question whether SGV specifically store catecholamines also in the modified adrenergic fibres has been investigated in KMnO4 fixed material. These results show that beside a large number of fibres in which there is a strict correlation between labeling and SGV, some fibres containing SGV do not retain the 3H-NA. Conversely some fibres which contain mainly agranular vesicles display radioautographic reaction. Therefore, in case of ligated fibres, SGV cannot be considered the specific organelles for storage of catecholamines. The axonal migration of labeled catecholamines has been studied in animals pretreated with IMAO. A moderate, but selective, labeling is present in the proximal portion of sciatic fibres of rats in which administration of labeled catecholamine preceeded of 2 hours the ligature and this was performed 22 hours before fixation. From these combined types of experiments, it is concluded that despite the presence of all the structures necessary for the storage of a high amount of catecholamines in the modified adrenergic fibres, only a small fraction of catecholamines accumulated above the ligature has been transported by axonal migration. Therefore, the axonal migration of catecholamines appears as an epiphenomenon related to the distal migration of enzymatic and storage proteins from the perikaryon.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00307098
