NMDA receptor function is enhanced in the hippocampus of aged rats |
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Authors: | Mariangela Serra Cristina Antonella Ghiani Maria Cristina Foddi Costantino Motzo Giovanni Biggio |
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Institution: | (1) Department of Experimental Biology Bernardo Loddo , University of Cagliari, Via Palabanda 12, 09123 Cagliari, Italy |
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Abstract: | The density and functional activity of theN-methyl-D-aspartate (NMDA)-sensitive glutamate receptor was examined in various brain areas of 3-, 18- and 24-month-old rats. The total numbers of binding sites for the NMDA receptor antagonists 3H]CGP 39653 and 3H]MK 801 binding sites were decreased in the hippocampus, cerebral cortex and striatum of 18- and 24-month-old rats, relative to 3-month-old animals. In the hippocampus of 18-month-old rats, the reduced number of NMDA receptors was associated with an increased sensitivity of 3H]MK 801 binding to the stimulatory action of glycine and glutamate. Thus, 10 M glycine and 10 M glutamate increased 3H]MK 801 binding in the hippocampus of 18-month-old rats by 75 and 160%, respectively; in 3-month-old animals, the same concentration of these amino acids increased binding by 37 and 95%, respectively. The sensitivity of 3H]MK 801 binding to glycine and glutamate was not increased in the cerebral cortex and striatum of aged rats. Moreover, an increased efficacy of glycine and glutamate in stimulating the binding of 3H]MK 801 in the hippocampus was no longer apparent in the 24-month-old rats. The increased sensitivity of 3H]MK 801 binding to glycine and glutamate in the hippocampus of 18-month-old rats may reflect an increase in NMDA receptor activity to compensate for the decrease in receptor number. |
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Keywords: | Aging [3H]CGP 39653 binding [3H]MK 801 binding NMDA receptor complex glutamate glycine rat brain |
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