Differential effect of aging on 3H-SCH 23390 binding sites in the retina and in distinct areas of the rat brain.
The effects of age on the binding parameters of the selective D-1 dopamine (DA) receptor antagonist 3H-SCH 23390 were studied in membrane preparations from rat striatum, substantia nigra, olfactory tubercle, prefrontal cortex and retina. When compared with 3-month-old animals, there was a significant decrease in the density of 3H-SCH 23390 binding sites in the striatum (-25%), substantia nigra (-24%), and olfactory tubercle (-23%), but not in the prefrontal cortex of senescent (23-month-old) rats. The affinity of 3H-SCH 23390 for D-1 DA receptors did not change with age in any of the brain areas analyzed. In contrast, the density of 3H-SCH 23390 binding sites was higher (+53%) in the retina of aged rats that in 3-month-old controls. Confirming previous studies, we observed that light deprivation induced a significant increment in the density of 3H-SCH 23390 binding sites in the retina of adult rats (+31%) but not in the retina of aged animals. The ability of light exposure to activate DAergic neurons in the rat retina was not altered by normal aging. In fact, a similar increase in the concentration of DOPAC was observed in the retina of light-adapted adult and senescent rats when compared to their respective dark-adapted controls (+94% and +95%, respectively). The results indicate that aging has a differential effect on D-1 DA receptors in the retina and different areas of the rat brain. Finally, the age-related increment in the density of retinal D-1 DA receptors does not appear to depend on presynaptic mechanisms, since DA metabolism is increased by light to the same extent in young and aged rats.
Giorgi
O
O
Department of Experimental Biology, University of Cagliari, Italy.
Porceddu
M L
ML
Pepitoni
S
S
Serra
G P
GP
Toffano
G
G
Biggio
G
G
D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001552:Benzazepines / Q000378:metabolism*; D001923:Brain Chemistry; D002540:Cerebral Cortex / Q000737:chemistry; D003342:Corpus Striatum / Q000737:chemistry; D004298:Dopamine / Q000032:analysis; D008027:Light; D008297:Male; D009830:Olfactory Bulb / Q000737:chemistry; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D012160:Retina / Q000378:metabolism* / Q000528:radiation effects; D013378:Substantia Nigra / Q000737:chemistry
D001552:Benzazepines; D011954:Receptors, Dopamine; D015102:3,4-Dihydroxyphenylacetic Acid; D004298:Dopamine