The effects of monoamine neurotoxins on peptides in the rat spinal cord.
The coexistence of two neuronally-localised peptides, substance P and thyrotropin-releasing hormone (TRH), in descending serotoninergic nerve fibres to the spinal cord was investigated using immunocytochemical and biochemical methods. Substance P-like material in the spinal cord was shown to be identical to the undecapeptide substance P by the criteria of gel filtration, high performance liquid chromatography and behaviour in substance P specific radioimmunoassays. Immunocytochemical staining for 5-hydroxytryptamine, substance P, and TRH showed that all three substances had a similar distribution in nerve fibres and terminals in the ventral and lateral grey matter of the spinal cord. After treatment with the serotonin neurotoxin 5,7-dihydroxytryptamine, neuronal elements containing 5-hydroxytryptamine, substance P and TRH degenerated and disappeared from these parts of the spinal cord in parallel with one another. Biochemical measurements of 5-hydroxytryptamine, substance P and TRH in the spinal cord after treatment with 5,7-dihydroxytryptamine confirmed that these three substances were all depleted from the ventral horn and, in addition, showed that there was a small depletion of substance P from the dorsal horn. Two other neuropeptides, somatostatin and methionine-enkephalin were not depleted from the spinal cord by treatment with 5,7-dihydroxytryptamine nor was substance P in other parts of the brain. Substance P in the spinal cord was unaffected by 6-hydroxydopamine, a drug known to destroy catecholamine-containing neurones. These results are consistent with coexistence of substance P and TRH together with 5-hydroxytryptamine in the descending axons and terminals of bulbospinal neurones.
D015115:5,6-Dihydroxytryptamine / Q000494:pharmacology*; D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004102:Dihydroxytryptamines / Q000494:pharmacology*; D008297:Male; D009434:Neural Pathways / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism
D004102:Dihydroxytryptamines; D010455:Peptides; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D013373:Substance P; D013973:Thyrotropin-Releasing Hormone; D015115:5,6-Dihydroxytryptamine