DEAFFERENTATION-INDUCED CHANGES IN NEUROPEPTIDES OF THE ADULT-RAT DORSAL HORN FOLLOWING PRONASE INJECTION OF THE SCIATIC-NERVE

The effect of deafferentation on the neuropeptides substance P (SP), c alcitonin gene-related peptide (CGRP), somatostatin (SS), and cholecys tokinin (CCK) in the lumbar dorsal horn of the adult rat was examined by the indirect immunohistochemical method. Deafferentation was induce d by injecting the sciatic nerve of anesthetized rats with proteolytic enzymes (20 mg pronase), which cause selective death of the nerve's g anglion cells and degeneration of their terminal arborization in the s pinal cord. The density of immunolabel of each peptide was determined by using a computerized densitometry analysis system in two animal gro ups, i.e., short-term (10-13 days after injection) and long-term (4-9 months). In both groups, the deafferentation produced a significant ip silateral depletion of CGRP, SP, CCK, and SS immunoreactivity. This de pletion was limited to the area occupied by the sciatic terminals in t he dorsal horn. In the long-term group, the loss of CGRP and SP staini ng was significantly less than that in the short-term animals, thus in dicating partial recovery. A similar, but not statistically significan t, trend was observed for CCK and SS. The large decrease in CGRP and S P seen in short-term animals reflects the large contribution of the sc iatic nerve to the lumbar dorsal horn. The partial recovery of peptide s demonstrates the plasticity of the nervous system and may parallel s prouting of primary afferents from other nerves, such as the saphenous nerve, as we have demonstrated in previous studies. (C) 1993 Wiley-Li ss, Inc.