Age-related changes in glutamate receptors: An autoradiographic analysis

The aim of the present study was to evaluate age-related changes in NMDA and AMPA receptors in old female rats. To this end a quantitative autoradiography of [H-3]-MK-801 and [H-3]-AMPA binding was performed in the brain of young (3-month-old), middle-aged (12-month-old) and old (36-month-old) rats. Moreover, the binding of [H-3]-spiperone to D-2 dopamine receptors was also examined. No changes were observed in the binding of [H-3]-MK-801 or [H-3]-AMPA in middle-aged rats compared to young ones. In the caudate-putamen and shell and core of the nucleus accumbens septi of old rats, a pronounced decrease in the [H-3]-MK-801 binding and a decreasing tendency in the [H-3]-AMPA binding were observed. Furthermore, the binding of [H-3]-MK-801 and [H-3]-AMPA was reduced in the hippocampal formation and, additionally, a marked decline in the [H-3]-MK-801 binding in different parts of the cerebral cortex including the frontal, parietal, cingulate, pyriform and insular cortices was found. The [H-3]-spiperone binding progressively decreased with age in the dorsolateral, ventrolateral and medial caudate-putamen. The present results show that aging processes lead to changes in the binding of both [H-3]-MK-801 to NMDA and [H-3]-AMPA to AMPA receptors in a number of structures, a phenomenon which may reflect motor and memory disturbances found in old rats and elderly humans.