THE EXPRESSION OF DIFFERENT CYTOCHEMICAL MARKERS IN NORMAL AND AXOTOMISED DORSAL-ROOT GANGLION-CELLS PROJECTING TO THE NUCLEUS GRACILIS IN THE ADULT-RAT

Rat lumbar dorsal root ganglion neurones projecting to the nucleus gra cilis in the brainstem were retrogradely labelled with Fluoro-Gold and analysed immunocytochemically for their expression of substance P-, c alcitonin gene-related peptide-, galanin-, galanin message-associated peptide-, neuropeptide Y-, nitric oxide synthase- and carbonic anhydra se-like immunoreactivity as well as affinity to Griffonia (bandeiraea) simplicifolia lectin I - isolectin B-4, RT97 and to choleragenoid. Th e analysis was made both in uninjured rats and in rats which had been subjected to unilateral sciatic nerve transection and partial resectio n 3 weeks earlier. The data showed that 6% of the L4 and L5 lumbar dor sal root ganglion cells that projected to the nucleus gracilis showed substance P-like immunoreactivity. Following nerve injury, none of the nucleus gracilis-projecting dorsal root ganglion cells showed substan ce P-like immunoreactivity. Nineteen per cent of the investigated cell population showed calcitonin gene-related peptide-like immunoreactivi ty in uninjured rats, but no nucleus gracilis-projecting calcitonin ge ne-related peptide-positive cells were found after nerve injury. Galan in- and, galanin message-associated peptide-like immunoreactivity were found in 2% and 3%, respectively, of the Fluoro-Gold-labelled cell po pulation normally and in 22% and 14%, respectively, after injury. No n europeptide Y-positive cells were found in the Fluoro-Gold labelled ce ll population normally, but after nerve injury, 96% of this population became neuropeptide Y-positive. Nitric oxide synthase-like immunoreac tivity was found in 2% of the FluoroGold-labelled cells normally and i n 10% after injury. Two per cent of the Fluoro-Gold-labelled cells in the normal cases were stained by Griffonia (bandeiraea) simplicifolia lectin I - isolectin B-4. After injury, however, no such double labell ing was found. Thirty-four per cent of the Fluoro-Gold-labelled cell p opulation was carbonic anhydrase positive normally, and 42% after inju ry. Seventy-five per cent of the Fluoro-Gold-labelled cells showed RT9 7 immunoreactivity normally and 12% after injury. Choleragenoid-like i mmunoreactivity was found in 99% of the Fluoro-Gold-labelled dorsal ro ot ganglion cells normally and 81% after injury. Immunohistochemical v isualisation of choleragenoid transganglionically transported from the injured sciatic nerve combined with neuropeptide Y immunocytochemistr y showed that primary afferent fibres and terminals in the nucleus gra cilis contain neuropeptide Y following peripheral nerve transection. T aken together, the results indicate that peripherally axotomised nucle us gracilis-projecting neurones undergo marked alterations in their cy tochemical characteristics, which may be significant for the structura l and functional plasticity of this system after injury.-