Alterations of central nervous system protein synthesis in response to spinal cord hemisection

This investigation explores the central nervous system protein-synthetic responses to hemisection of the spinal cord. Adult male rats hemisected at mid T2 were given intravenous injections of 14C-leucine at 0.7, 30, or 70 days postoperative. Four hours later the T1, T2, T3, and C6 segments of the spinal cord and right and left samples of somatomotor and occipital cortex were removed, weighed, and frozen. These samples were later homogenized and subjected to trichloroacetic acid (TCA) separations. Protein-synthetic activity was expressed as the ratio of the specific activity of the TCA precipitable proteins to the specific activity of the TCA free amino acid pool. In the spinal cord samples protein-synthetic activity was greater than in controls at 7 and 30 days postoperative in the T2 segment and at 30 days postoperative in the C6 and T3 segments. In the cortical samples protein-synthetic activity was greater than in controls in the right and left somatomotor cortex at 30 days postoperative, while it was less than in controls in the left somatomotor cortex at 70 days postoperative. Thus, T2 hemisection leads to initial increases and subsequent decreases in protein-synthetic activity in both spinal cord and somatomotor cortex. These results are discussed in terms of possible regenerative neural reactions occurring in the central nervous system following spinal cord injury.