ISSN:
0003-276X
Keywords:
Rat
;
Aging
;
Light morphometric
;
Degeneration
;
Ultrastructural
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
The suprachiasmatic nucleus (SCN) is a principal controller of mammalian circadian rhythms. However, in spite of documented disturbance of biological rhythms in old animals, few significant age-related changes have been observed in this nucleus. This study examined age-related differences in SCN volume, neuronal number, density, and ultra-structural features in the entire rat SCN and in its two divisions, the denser ventromedial (compacta) and less dense dorsolateral (dissipata). Light and electron microscopic morphometric techniques were utilized in weanlings (21-28 days), young adults (3-6 mo), and aged (30-36 mo) animals.The total SCN volume, as well as volumes of-the compacta regions, were significantly greater in young adult and aged rats than in weanlings. Thus, as the rat ages the SCN increases in total size. However, the dissipata region appears to decrease in volume while the compacta increases. Even though the total number of SCN neurons was quite constant in the three age groups, the number of neurons in the dissipata region was decreased significantly in the young adult and aged groups as compared to the weanling.Neurons in the compacta region were usually spindled-shaped with two dendritic processes, while oval to spheroidal cells with 3-4 processes predominated in the dissipata. Nuclei of SCN cells were often invaginated. In weanlings, more SCN neuronal nuclei had invaginated nuclei in the dissipata region (66%) compared to the compacta (37%). In the two older age groups of rats, a higher percentage of invaginated neuronal nuclei were found in both regions. However, more were still found in the dissipata (90%) compared to the compacta (72%), even though the number of these cells in the compacta doubled. Thus, there was a large increase in the number of invaginated nuclei, as well as the number of invaginations, in the young adult rats compared to the weanling group, and this increase persisted in aged rats.SCN neurons usually had nuclei surrounded by a thin perimeter of cytoplasm containing sparse mitochondria and granular endoplasmic reticulum, multiple Golgi regions, and a moderate number of free ribosomes. In weanlings, mitochondria contained dense cristae and the granular endoplasmic reticulum was relatively prominent. Degenerative ultrastructural changes which included mitochondrial enlargement/vacuolation, Golgi vacuolation, lysosome, and lipofuscin development occurred in less than 10% of young adult SCN cells, and were more frequently found in the dissipata. In aged, rats 30% of the neurons showed degenerative changes in the dissipata compared with 18% in the compacta. Degenerative changes appeared highly correlated with the degree of membrane folding. Ultrastructural degenerative cell changes and light microscopic morphometric observations are discussed in relation to loss of circadian rhythms with advancing age. © 1993 Wiley-Liss, Inc.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/ar.1092370108
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