Microanatomical changes in the frontal cortex of aged rats: effect of L-deprenyl treatment.

The present study was designed to assess whether treatment with L-deprenyl has any effect on the age-related microanatomical changes in the rat frontal cortex. Male Sprague-Dawley rats of 19 months of age were treated until the 24th month with an oral daily dose of 1.25 mg/kg or of 5 mg/kg of L-deprenyl. Eleven-month-old untreated rats were used as an adult reference group. The density of nerve cell profiles and of glial fibrillary acidic protein-(GFAP) immunoreactive astroglial profiles, lipofuscin accumulation within the cytoplasm of pyramidal neurons, and MAO-B reactivity were assessed. A decreased density of nerve cell profiles and an increased density of astroglial profiles as well as augmented lipofuscin deposition and MAO-B reactivity were observed in the frontal cortex of rats of 24 months in comparison with 12-month-old animals. In the frontal cortex of rats treated with 5 mg/kg/day L-deprenyl, which is a dose inhibiting MAO-B activity, the density of nerve cell and GFAP-immunoreactive astrocyte profiles is increased and decreased respectively in comparison with age-matched untreated subjects. Lipofuscin deposition is reduced. The lower dose of L-deprenyl (1.25 mg/kg/day) which did not affect MAO-B activity, decreased lipofuscin deposition but was without effect on the density of nerve cell or GFAP-immunoreactive astrocyte profiles. The above findings suggest that treatment with L-deprenyl is able to counter some microanatomical changes occurring in the frontal cortex of aged rats. Some of these effects are probably not related to the inhibitory MAO-B activity of the compound.