Age-related changes in the turnover rates of D1-dopamine receptors in the retina and in distinct areas of the rat brain.
The steady-state density and the turnover rates of D1-dopamine receptors were investigated in the striatum, nucleus accumbens, substantia nigra, and retina of adult (3-month-old) and aged (23-month-old) rats. The turnover rates were measured by monitoring the repopulation kinetics of D1-dopamine receptors labeled with [3H]-SCH 23390 after the irreversible inactivation induced by a single dose of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ, 10 mg/kg, s.c.). In all the neural tissues examined, the repopulation of D1 dopamine receptors could be adequately described by a theoretical model that assumes a constant rate of receptor production (i.e. zero order) and a rate of degradation that is dependent on the receptor density at any time (i.e. first order). The results obtained indicate that the reduction in the density of D1-dopamine receptors in the striatum, nucleus accumbens and substantia nigra of aged rats is the result of a larger decrease in the receptor production rate (-44 to -60%) than in the receptor degradation rate (-21 to -46%). By contrast, the production rate of D1-dopamine receptors in the retina of aged rats remains unchanged, whilst the degradation rate is reduced by 25%. This results in an age-related increase in the density of D1-dopamine receptors in the rat retina.
Department of Experimental Biology, University of Cagliari, Italy.
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Giorgi
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Pibiri
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Dal Toso
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Ragatzu
D000317:Adrenergic alpha-Antagonists / Q000633:toxicity; D000375:Aging; D000818:Animals; D001552:Benzazepines / Q000378:metabolism; D001921:Brain / Q000254:growth & development* / Q000378:metabolism; D002375:Catalepsy / Q000139:chemically induced / Q000503:physiopathology; D003342:Corpus Striatum / Q000254:growth & development / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009714:Nucleus Accumbens / Q000254:growth & development / Q000378:metabolism; D009928:Organ Specificity; D011804:Quinolines / Q000633:toxicity; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017447:Receptors, Dopamine D1; D012160:Retina / Q000254:growth & development* / Q000378:metabolism; D013378:Substantia Nigra / Q000254:growth & development / Q000378:metabolism; D013997:Time Factors
D000317:Adrenergic alpha-Antagonists; D001552:Benzazepines; D011804:Quinolines; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; C000470:EEDQ