Ischemia-induced changes in brain monoamine metabolism in aged spontaneously hypertensive rats.

Effects of aging on monoamine metabolism in transient cerebral ischemia were studied using adult and aged female spontaneously hypertensive rats (SHRs). Tissue monoamine contents in discrete brain areas were quantified after 20 min of cerebral ischemia with or without 30-min recirculation. Cerebral blood flow (CBF) was determined with a hydrogen clearance method in separate experiments. Dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) contents in the striatum, nucleus accumbens and septum decreased in ischemic aged SHRs, compared with those in ischemic adult SHRs. After 30-min recirculation, DA contents were actually unchanged with inconsistently increased DOPAC levels. Ischemic CBF decreased to < 20% of the resting CBF in the striatum and cortex, which was not different between the two age groups of SHRs. These results indicate that aging is primarily responsible for more severely impaired DA metabolism during cerebral ischemia in aged SHRs.