The postnatal evolution of local cerebral metabolic rates for glucose (LCM-Rglcs) and of regional rates of cerebral uptake of beta-hydroxybutyrate (beta HB) were studied in the suckling rat between postnatal days (P) 10 and 21. LCM-Rglcs were low and homogeneous at P10. They increased significantly in 4 auditory regions between P10 and P14 at the time of maturation of the auditory function. Between P14 and P17, they increased further in 2 auditory regions, in 1 visual area, the lateral geniculate nucleus, and 3 limbic and 3 motor areas. These increases occurred simultaneously with the maturation of vision and with the development of the rat locomotion and behavioral activities. Between P17 and P21, LCMRglcs increased in all areas studied. Conversely to the function-related increases in LCMRglcs, regional rates of cerebral beta HB uptake showed an overall increase between P10 and P14, stayed very high until P17 and did not correlate with the maturation of the rat behavior. Between P17 and P21, rates of cerebral beta HB uptake decreased significantly in all regions studied. In conclusion, it appears that, even in the rat whose cerebral metabolic activity depends upon both glucose and ketone bodies during suckling, postnatal increases in LCMRglcs represent a signal of the acquisition of new functions and neurological competence.