Porceddu M L, De Montis G, Pepitoni S, Toffano G, Biggio G
Department of Experimental Biology, University of Cagliari, Italy.
Neurobiol Aging. 1990 Mar-Apr;11(2):105-9. doi: 10.1016/0197-4580(90)90042-x.
The effect of aging on the binding parameters of 3H-SCH 23390, the most selective ligand of D-1 DA receptors, was studied in membrane preparations from the rat retina. DA-stimulated adenylate cyclase activity was also measured in order to better characterize the changes in retinal D-1 DA receptors induced by aging. The binding studies revealed that the density of 3H-SCH 23390 was increased (34 and 73%) in the retina of 14- and 26-month-old rats, when compared to young adult animals, respectively. In contrast, aging failed to alter the sensitivity of the adenylate cyclase to the action of DA. In fact, DA (10(-6) M to 10(-4) M) elicited a similar enhancement in cyclic AMP formation in retinal homogenates of both adult and senescent rats. Since dark adaptation increases the density of D-1 DA receptors in the retina of adult rats we studied the effect of light deprivation on 3H-SCH 23390 binding and DA-sensitive adenylate cyclase activity in the retina of senescent rats. As previously shown (25) light deprivation increased 3H-SCH 23390 binding and enhanced DA-sensitive adenylate cyclase activity in the retina of young adult rats. On the contrary, dark adaptation failed to increase 3H-SCH 23390 binding and to enhance DA-sensitive adenylate cyclase activity in the retina of senescent rats. Taken together these results indicate that D-1 DA receptors in the retina of aged rats have biochemical and functional properties different from those found in the retina of adult animals; these changes may result in an altered response to the physiological stimuli elicited by environmental lighting.
在大鼠视网膜的膜制剂中研究了衰老对3H-SCH 23390（D-1多巴胺受体最具选择性的配体）结合参数的影响。还测量了多巴胺刺激的腺苷酸环化酶活性，以便更好地表征衰老引起的视网膜D-1多巴胺受体的变化。结合研究表明，与年轻成年动物相比，14月龄和26月龄大鼠视网膜中3H-SCH 23390的密度分别增加了34%和73%。相反，衰老并未改变腺苷酸环化酶对多巴胺作用的敏感性。实际上，多巴胺（10^(-6) M至10^(-4) M）在成年和衰老大鼠的视网膜匀浆中引起的环磷酸腺苷形成的增强相似。由于暗适应会增加成年大鼠视网膜中D-1多巴胺受体的密度，我们研究了光剥夺对衰老大鼠视网膜中3H-SCH 23390结合和多巴胺敏感的腺苷酸环化酶活性的影响。如先前所示（25），光剥夺增加了年轻成年大鼠视网膜中3H-SCH 23390的结合并增强了多巴胺敏感的腺苷酸环化酶活性。相反，暗适应未能增加衰老大鼠视网膜中3H-SCH 23390的结合，也未能增强多巴胺敏感的腺苷酸环化酶活性。综合这些结果表明，老年大鼠视网膜中的D-1多巴胺受体具有与成年动物视网膜中不同的生化和功能特性；这些变化可能导致对环境光照引起的生理刺激的反应改变。
