Alterations of brain insulin receptor characteristics in aging mice.

An interesting role of insulin and insulin receptors (InsRs) in the brain is neuromodulation of monoaminergic systems. Since our previous studies showed age-dependent alterations of alpha- and beta-adrenoceptors in mouse brain cortex, the intriguing role of brain InsRs per se and their involvement in adrenergic modulation prompted us to check their eventual changes with aging. Thus, brain InsR characteristics were studied in young (3 months) and old (27 months) Balb/c-nu mice by direct binding with (125)I-insulin. A two-sites model analysis of data shows a statistically significant age-related decrease of receptor density (39%) and k(d) (57%) in the high affinity population. The low affinity receptor subset also shows a decreasing trend of its characteristics; however, differences are not statistically significant and show a high degree of interindividual variability in both groups of mice.