ISSN:
1573-6830
Keywords:
axonal transport
;
glycine
;
Aplysia
;
identified cells
;
retrograde axonal transport
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary 1. The specific retrograde axonal transport of free glycine within the identified neurons R3-14 ofAplysia californica was studied. 2. The soma of the R3-14 neurons are located in the parietovisceral ganglion and their axons project down the branchial nerve to end in a large peripheral field. Using a double-chambered apparatus, the peripheral tissue was incubated in medium containing a3H-amino acid for 4–48 hr, while the nerve and ganglion were isolated and perfused with plain or chemically altered medium. The nerve and ganglion were then either rapidly frozen for scintillation counting or fixed for autoradiography. 3. When3H-glycine was used, radioactivity entered the nerve rapidly, reached the ganglion in 3 hr, and was transported largely (〉80%) in the free amino acid form [trichloroacetic acid (TCA) soluble]. The right parietovisceral hemiganglion accumulated up to nine times more radioactivity than the left hemiganglion, reflecting the presence of the R3-14 axons and soma. Two phases of radioactivity were observed, a fast component moving at about 3 mm/hr and a slower (but larger) component moving at about 0.4 mm/hr. 4. Light microscope autoradiography on nerves containing3H-glycine revealed that the R3-14 axons accounted for more than 30% of the total label in the nerve but occupied less than 7% of the total cross-sectional area of the axonal core. Electron microscope autoradiography showed a close association of silver grains and dense core vesicles in the R3-14 axons. 5. Retrograde axonal transport of free glycine was inhibited by (in decreasing order of effectiveness) mercuric chloride, vinblastine, colchicine, Nocodazole, and 2,4-dinitrophenol (2,4-DNP). 6. Comparative studies of other amino acids [3H-leucine,3H-serine,3H-glutamic acid,3H-γ-aminobutyric acid (3H-GABA), and3H-alanine] showed that3H-glycine is the only amino acid that is rapidly axonally transported in large quantities within the R3-14 axons. 7. This work demonstrates, for the first time, that a free amino acid, glycine, is transported in the retrograde direction within a select group of axons. The significance of this transport of glycine is discussed in relation to its use as a neural messenger by neurons R3-14.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00733587
Permalink