A study on the pattern of alkaline phosphatase activity correlated with observations on silver-impregnated structures in the developing mouse brain.

Alkaline phosphatase activity was localised in specific groups of cellular processes, nuclei and fibre tracts in fetal mouse brain at 9.5-17.5 days post coitum. A radial band of intense enzymatic activity extended longitudinally within the rhombencephalon at 10.5 to 15.5 days. This enzymatic band was topographically related to the efferent nuclei of the cranial nerves, except those nuclei which had migrated laterally to their final positions. The enzymatic activity was seen in some but not all silver-impregnated fibre tracts that appeared early in development, but such association disappeared upon further maturation of the brain. Alkaline phosphatase activity may be related to an enhanced metabolism occurring during the formation of the cranial nerve efferent nuclei and the establishment of neuronal connections in the fetal brain.