Ontogenetic changes in myelin protein composition in different regions of rat central nervous system.

Developmental changes in protein composition of myelin obtained from whole brain of various species were the subject of several studies in recent years 1-3. By contrast, very little was been published on the composition of myelin proteins derived from forebrain 4 and from spinal cord 4~7. In relation to possible specific function of myelin in various regions of the central nervous system (CNS) and in relation to its different ontogenetic development the possibility existed that different compositional profiles of rat myelin proteins could be found in developing forebrain, cerebellum and spinal cord. Therefore, myelin was isolated from these regions of rat CNS by a slight modification of the Norton procedure8. Myelin proteins were ex­ tracted with sodium dodecyl sulfate and separated by disc electrophoresis on polyacrylamide gels as described 9. By scanning the gels the composition of myelin proteins was studied between the 5th (spinal cord), 10th (cerebellum) and 15th day (forebrain), and the 90th day of rat life and was compared with that of adults. During development of rat CNS there was a marked decrease in the larger basic protein L 6 and a concomitant increase in the smaller basic protein S 6 in all regions studied, e. g., L of forebrain de­ creased in relation to total protein from around 34% to 18% and S increased from about 25% to 39% in 15-day-old and 60-day-old animals, respec­ tively, based on staining with Coomassie Blue. The composition of myelin basic proteins for adult fore-