Effect of chronic morphine administration on measured levels and chromatographic characterization of six neuropeptides in guinea-pig ileum.
Guinea-pigs were chronically treated with morphine by subcutaneous implantation of a compounded morphine pellet. After 7 days, the animals were sacrificed, and the small intestine was removed and extracted for the assay of 6 neuropeptides (substance P, vasoactive intestinal peptide, galanin, dynorphin A (1-8), dynorphin A (1-17) and alpha-neo-endorphin). The neuropeptide content of the extracts was measured by radioimmunoassay, and the extracts were subjected to analysis by reversed-phase high pressure liquid chromatography. The measured level of each neuropeptide was not significantly different from that in a control group of animals, and the chromatographic elution pattern obtained for each peptide was also similar in control and morphine-treated animals. Furthermore, the major peak of immunoreactivity for each peptide occurred with approximately the same retention time as synthetic standards having the porcine sequence for that peptide. It is concluded that chronic morphine treatment does not alter the tissue concentration or molecular form of at least 5 of the 6 neuropeptides studied. In the case of a alpha-neo-endorphin, a peak of immunoreactivity was discovered that did not correspond to the synthetic peptide. The amount of immunoreactive material present in this peak varied with oxidation and so its contribution to the assay results could not be calculated.
Shuttleworth
C W
CW
Department of Anatomy and Histology, School of Medicine, Flinders University, Bedford Park, Australia.
Murphy
R
R
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004343:Drug Implants; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects*; D066298:In Vitro Techniques; D009020:Morphine / Q000494:pharmacology*; D009479:Neuropeptides / Q000032:analysis*; D011863:Radioimmunoassay
D004343:Drug Implants; D009479:Neuropeptides; D009020:Morphine