RESUMO
A comparative study using membrane homogenate binding, autoradiography, and Western blot assays was carried out to determine the age-related changes in N-methyl-D-aspartate (NMDA) receptors in 4-, 12- and 24-month-old male Wistar rats, treated or not with vitamin E. Vitamin E treatment was 20 mg/kg i.p. daily for 15 days. [(3)H] 5-methyl-10,11-dihydro-5H-dibenzo (a,d) cycloheptan-5,10-imine maleate (MK-801) binding was significantly increased in all areas studied (cortex and hippocampus) at all ages when rats received this treatment. A Western blot study in vitamin-E-treated rats and their controls did not reveal significant differences in the amounts of NR2A, an NMDA receptor subunit widely distributed in the brain mainly in cortex and hippocampus. We conclude that the effect of vitamin E on NMDA receptors is largely age independent. Previous reports and our data have described the presence of age-dependent NMDA receptor changes. The effect of vitamin E in aging is considered to be mediated by free radical scavenging, but from our data, we conclude that this mechanism is not relevant for age-dependent NMDA receptor changes. Our results also support that age or vitamin E treatment have no relevant effects on NR2A subunit, at least until 24 months in rats.
