A serotonin synthesis inhibitor, p-chlorophenylalanine reduces the heat shock protein response following trauma to the spinal cord: an immunohistochemical and ultrastructural study in the rat.

The influence of the serotonin synthesis inhibitor, p-CPA on the expression of the heat shock protein (70 kDa), which occurs around an injury to the rat spinal cord, was examined by immunohistochemistry. A longitudinal incision was made into the right dorsal horn at the T10-11 level. Five hours later samples were removed from the T9 and T12 segments. Samples from untreated traumatised animals showed signs of edema and many distorted neurons, particularly in the ipsilateral grey matter. Neurons of the same regions showed a profound increase in HSP-70 immunostaining compared with intact controls. At ultrastructural level, the immunoreactivity was detected in neuronal cytoplasm attached to the surface of organelles including endoplasmic reticulum, in the nucleus and in dendrites. Other groups of rats were given p-CPA before injury to reduce the synthesis of serotonin and to minimise its stores in the cord. The HSP-immunostaining in neurons of the T9 and T12 segments of the spinal cord was virtually lacking in the drug treated animals. The signs of edema and the structural changes of these segments were markedly reduced. The results show that inhibition of serotonin synthesis prior to the traumatic insult has an inhibitory influence on HSP response occurring in neurons around the site of injury to the spinal cord, not reported earlier.