A new experimental animal for the study of age-related changes in serotonergic neuronal activity in the brain cortex.

Calcium uptake by the cortical synaptosomes in a rodent (Fischer rat) and an insectivore shrew (Suncus murinus) was detected as a parameter reflecting molecular dysfunction of the aging brain. The change in calcium uptake by the cortical synaptosomes in both species was concomitant which showed less than half the capacity at 24 months old animals compared with those at 8 months old. On the other hand, 5-hydroxytryptamine binding and imipramine binding to the membrane fraction of aging rat brain cortex was not altered in terms of binding capacity along with aging, while, in Suncus, the binding of both serotonergic ligands declined with aging. In order to elucidate decreased serotonergic activity in human demented aged brain, together with declining activity in neurotransmitting systems detectable as a function of calcium uptake by the cortical synaptosomes, Suncus may be an appropriate animal model for studying physiological aging processes in the mammalian brain cortex.