Summary:The postnatal changes in local cerebral blood flow in freely moving rats were measured by means of the quantitative autoradiographic e 4C]iodoantipyrine method. The animals were studied at 10, 14, 17, 21, and 35 days and at the adult stage. At 10 days after birth, rates of blood flow were very low and quite homogeneous in most cerebral structures except in a few posterior areas. From these relatively uniform levels, values of local ce rebral blood flow rose notably to reach a peak at 17 days in all brain regions studied. Rates of blood flow decreased between 17 and 21 days after birth and then increased from weaning time to reach the known characteristic dis tribution of the adult rat. The postnatal evolution of local cerebral blood flow in the rat is in good agreement with Local cerebral blood flow (LCBF) techniques have been extensively used to map changes in ce rebral metabolic rate in a variety of animal species including rat, cat, piglet, sheep, dog, monkey, and humans (Ca vazutti and Duffy, 1982; Flecknell et aI., 1983; Hascoet et aI. , 1988; Hosokawa et aI. , 1977; Kennedy et aI., 1972;Lassen and Ingvar, 1972; Plotkine et aI., 1986; Raichle et aI. , 1983; Reivich et aI., 1968 Reivich et aI., , 1969 Rosenberg et aI. , 1982; Sakurada et aI. , 1978;Sokoloff, 1961). Indeed, it has been shown in adult animals that in most phys iological or pharmacological states, functional ac tivity in the different structures of the central ner vous system regulates the local rate of energy me tabolism and that LCBF is coupled to local metabolic demand (Des Rosiers et aI., 1974; McCulReceived December 12, 1988; revised March 30, 1989; ac cepted April 7, 1989
579previous studies in other species such as dog and humans that also show higher rates of cerebral blood flow and glucose utilization at immature stages. However, in the rat, local cerebral blood flow and local cerebral glucose utilization are not coupled over the whole postnatal pe riod studied, since blood flow rates reach peak values at 17 days whereas glucose utilization remains still quite low at that stage. The high rate of cerebral blood flow in the 17-day-old rat may reflect the energetic and biosynthetic needs of the actively developing brain that are completed by the summation of glucose and ketone body utilization. Reivich, 1974;Sokoloff, 1961Sokoloff, , 1981. Studies performed in immature dogs (Gre goire et aI. , 1978) and in human infants and children (Chugani and Phelps, 1986; Chugani et aI., 1987;Kennedy and Sokoloff, 1957) were also able to show that, in newborns as in adults, cerebral blood flow and metabolism are tightly coupled.The e4C]iodoantipyrine autoradiographic method of Sakurada et al. (1978) requires catheterization of blood vessels in order to permit administration of the tracer and to facilitate collection of timed arte rial blood samples. For these reasons, this tech nique has been mostly used in animals of a quite large size such as adult rats (Ingvar et aI., 1981; McCulloch et aI. , 1982; Mraovitch et aI. , 1986) or c...