Rate of cerebral ATP utilization in rats 1

SAMSON, FREDERICK E., JR., WILLIAM M. BALFOUR AND NANCY A. DAHL. Rate of cerebral ATP utilization in rats. Am. J. Physiol. 1 g8( I) : 2 I 3-2 I 6. 1 g6o.-The rate of adenosinetriphosphate (ATP) disappearance in the brain after inhibition of aerobic and anaerobic metabolism was investigated. It was found that the rate increases with increasing age in the neonatal rat and that the effect of lowering the body temperature, which slows the rate, is greater in the 2 z-day rat than in the newborn. Calculation from the data gives 0.5 pM/sec/gm as the rate of high-energy phosphate utilization in the 2 ~-day rat, and 0.04 &sec/gm in the ~-day rat. This increase in the rate of energy utilization during neonatal maturation is compared with the capacity to generate ATP; the utilization increase is found to be six times that of the capacity to generate ATP. The QIO of the high-energy phosphate utilization in the 2 I -day rat is I .7 in the 37’-25OC range, but is IO. in the 25’-15Oc range. It is concluded that the rate of high-energy phosphate utilization is closely related to the amount of neuronal activity and, further, that the energy cost per average nerve impulse probably is greater in the adult brain than in the neonatal brain. It is easy to see that power is used in the contraction of the heart or the production of urine by the kidneys, but the power use by the brain is not as obvious. The synthetic processes of the brain will, of course, use some energy. However, it is reasonably certain that most of the energy expended goes into chemical concentration work (i.e. maintaining differential ion concentrations) (2) and ultimately leaves the brain as heat. Furthermore, the greater the amount of functional activity or ‘impulse density’ the greater the quantity of ions and compounds that must be returned to the average, ‘homeostasis’ concentration gradient.