The analgesic and respiratory depressant actions of metorphamide in mice and rabbits

Xu, Shao Fen; Lu, Wen Xiao; Zhou, Kai Rong; He, Xiao Pin; Shanfu, Niu; Xu, Wei; Zhang, An Zhong; Weber, Eckard; Chang, Jaw‐Kang

doi:10.1016/0143-4179(85)90103-9

Cited by 7 publications

(1 citation statement)

References 11 publications

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“…Some of these peptides have well-defined functions, but little characterization of metorphamide's physiological effects has yet been done. Preliminary experiments have shown that intracerebroventricular and intracisternal application of metorphamide in mice and rabbits produces naloxone-reversible analgesia, respiratory depression, and bradycardia (Xu et al, 1985). As analgesia is thought to be mediated by p opioid receptors, this finding may suggest an interaction of metorphamide with p opioid receptors under certain in vivo experimental conditions.…”

Section: Discussionmentioning

confidence: 99%

Distribution Pattern of Metorphamide Compared with Other Opioid Peptides from Proenkephalin and Prodynorphin in the Bovine Brain

Sonders

Weber

1987

Journal of Neurochemistry

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Metorphamide is a [Met]-enkephalin-containing opioid octapeptide with a C-terminal alpha-amide group. It is derived from proenkephalin and is, so far, the only endogenous opioid peptide with a particularly high affinity for mu opioid (morphine) receptors, a somewhat lesser affinity for kappa opioid receptors, and a relatively low affinity for delta opioid receptors. The concentrations of metorphamide in the bovine caudate nucleus, the hypothalamus, the spinal cord, and the neurointermediate pituitary were determined by radioimmunoassay and chromatography separation procedures. Metorphamide concentrations were compared with the concentrations of eight other opioid peptides from proenkephalin and prodynorphin in identical extracts. The other opioid peptides were [Met]-enkephalyl-Arg6-Phe7 and [Met]-enkephalyl-Arg6-Gly7-Leu8 from proenkephalin; alpha-neoendorphin, beta-neoendorphin, dynorphin A(1-8), dynorphin A(1-17), and dynorphin B from prodynorphin; and [Leu]-enkephalin, which can be derived from either precursor. All opioid peptides were present in all four bovine neural tissues investigated. Metorphamide concentrations were lower than the concentrations of the other proenkephalin-derived opioid peptides. They were, however, similar to the concentrations of the prodynorphin-derived opioid peptides in the same tissues. Marked differences in the relative ratios of the opioids derived from prodynorphin across brain regions were observed, a finding suggesting differential posttranslational processing. Differences in the ratios of the proenkephalin-derived opioids across brain regions were less pronounced. The results from this study together with previous findings on metorphamide's mu opioid receptor binding and bioactivities suggest that the amounts of metorphamide in the bovine brain are sufficient to make this peptide a candidate for a physiologically significant endogenous mu opioid receptor ligand.

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Section: Discussionmentioning

confidence: 99%