Decreased local cerebral blood flow in young and aged spontaneously hypertensive rats.

Abstract

Local cerebral blood flow (LCBF) was measured using the [14C] iodoantipyrine method in 76 discrete brain regions in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) of 4 months old (young-adult) and 16-17 months old (aged). Compared with the young-adult WKY, in both the young-adult and aged SHR, LCBF was reduced in scattered brain regions, in more wide-spread regions in the aged SHR, while LCBF was not significantly decreased in the aged WKY. The results indicate that, firstly, cerebral hypoperfusion is already established at the age of 4 months by persistent hypertension in SHR, but age-related decline of LCBF thereafter is not remarkable, and secondly, cerebral perfusion is preserved in normotensive WKY even in their senescence. Combined with the present results and the previous study that local cerebral glucose utilization (LCGU) reduced in the aged groups of WKY and SHR in scattered brain regions, more intensively and more extensively in the aged SHR, but did not in the young-adult SHR, the followings are suggested: 1) in the young-adult SHR, LCBF is decreased but brain metabolism is preserved in a state of misery perfusion, 2) in the normotensive aged WKY, LCBF is preserved but brain metabolism is reduced implying "primary hypometabolism during senescence", and 3) in the aged SHR, LCBF is decreased and brain metabolism is more severely reduced, probably resulting from a combination of the primary hypometabolism of the brain by aging and a secondary hypometabolism due to the long-standing hypertension related hypoperfusion.