T1 values of phosphomonoester and phosphocreatine of brain show no significant change during development.

Changes in apparent 31P spin-lattice relaxation times (T1) associated with brain development were investigated in rat pups. While analysis of variance showed strong age dependency in [PME]/[ATP] and [PCr]/[ATP], the T1 values of PME, PCr, and ATP did not show any age dependency. The studies indicate that in contrast to the data which indicated aging-related changes in the T1 values of PME, the observed changes in PME during neonatal development are likely to be quantitative in nature.