Decrease of phosphocreatine in regenerating neurons.

Earlier studies in this laboratory have dealt with the striking histological and chemical changes which occur in motoneurons of the spinal cord of the rhesus monkey after axon section and during the period of axon regeneration (l-3). The time course of the morphological changes has been analyzed, and the characteristics of hhese changes reviewed in a recent report (2). The evidence now at hand indicates that in the cell body the phenomenon of chromatolysis, or decrease in basophilic cytoplasmic Nissl substance, which occurs soon after axon section and is slowly reversed in the course of months, is accompanied by several important biological and chemical changes. These may be summarized briefly as follows: (1) The decrease of Nissl substance can be directly correlated with a decrease of cytoplasmic pentose nucleoprotein (1). (2) Acid phosphatase activity is especially increased in the cell body in the region of greatest nucleoprotein turnover (2), but is also increased in the regenerating ax0n.l (3) Cytochrome oxidase and succinic dehydrogenase activity in the cell body is decreased during the period of axon regeneration (3, 4). (4) Resistance to poliomyelitis virus activity is increased during the period of axon regeneration (5). (5) Reflex activity of regenerating neurons is reduced as compared with normal (6). The present report adds one more bit of evidence which may contribute toward our understanding of the complex processes involved in both the normal functioning of the neuron and in its regenerative activities. The finding of marked change in oxidative metabolism and of increased phosphatase activity in regenerating neurons suggested that the equilibrium of important energy-rich phosphate compounds might be shifted enough so that a determinable change in amount might occur. This has been found to be the case for phosphocreatine, and, although t,he mar prevented completion of the program originally planned, the results thus far obtained seem sufficiently important to be presented as they stand. Determinations of phosphocreatine, acid-hydrolyzable phosphorus, and inorganic phos-