Regional cerebral blood flow during development and ageing of the rat brain.

Regional cerebral blood flow (rCBF) in the conscious Fischer-344 rat was measured in 14 brain regions at 5 different ages. rCBF increased significantly (P less than 0.05) in most anterior brain regions between 1 and 3 months of age, but not in phylogenetically more primitive regions from the mid- and hindbrain that may have matured prior to 1 month of age. rCBF tended to increase or remain constant between 3 and 12 months, and rose significantly in the frontal lobe. Between 12 and 24 months of age, rCBF declined by an average of 17 per cent and fell significantly in 5 brain regions, mainly from the posterior brain, and in some, possibly in relation to partial functional deafferentation. There were no statistically significant changes in rCBF between 24 and 34 months of age. rCBF and local cerebral glucose utilization (LCGU) do not follow identical time courses during development and maturation of the rat brain. A fall in LCGU between 3 and 12 months of age, when rCBF remains constant or tends to rise, may reflect increased sensitivity of the cerebrovascular bed to metabolic factors which regulate cerebral blood flow.