| 1. |
- Bobrova, Irina, et al.
(author)
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A structure-activity study of nociceptin-(1-13)-peptide amide. Synthesis of analogues substituted in positions 0, 1, 3, 4 and 10.
- 2003
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In: European journal of medicinal chemistry. - 0223-5234. ; 38:7-8, s. 687-694
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Journal article (peer-reviewed)abstract
- A series of analogues of nociceptin, Noc(1-13)NH(2) (an agonist at the ORL1 receptor) was synthesized with following modifications: (1) N-terminal extension with Arg(0); (2) replacement of Gly(3) by basic or polar amino acids-Arg, Asn, Lys(For) or deletion; (3) exchange of Phe(1) or Phe(4) by Phe(NO(2)); (4) substitution of Ser(10) with D-Ser, Pro, D-Pro. The analogs were synthesized by solid-phase methodology using Fmoc-amino acid pentafluorophenyl esters. The affinity for the ORL1 and for the kappa, micro and delta-opioid receptors was investigated by radioligand binding assay and bioactivity by a mouse vas deferens (MVD) assay. The addition of the amino acid residue Arg to the N-terminal enhances the opioid receptor affinity of Noc(1-13)NH(2) while retaining ORL1 receptor affinity at a moderate level. The replacement of Gly in position 3 by the basic or polar amino acids-Arg, Asn, Lys(For) or its deletion led to inactive analogues. The replacement of Ser in position 10 by its D-isomer, Pro and D-Pro resulted in a series of analogues with the following order of activity: Ser(10)>D-Ser(10)>Pro(10)>D-Pro(10). In [D-Ser(10)]Noc(1-13)NH(2), introduction of an additional Phe(NO(2))(4) led to a >60-fold increase of ORL1 affinity, completely attenuating the loss of affinity brought about by Ser(10). In other analogues, introduction of Phe(NO(2))(4) did not change the magnitude of ORL1 binding significantly. Generally, while modifications in position 3 frequently led to a loss of most or all bioactivity, modifications in position 0 (Arg(0)) or 4 (Phe(NO(2))(4)) and 10 (D-Ser(10), Pro(10)) are tolerated.
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| 2. |
- Vlaskovska, Mila, et al.
(author)
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Opiate modulation of dynorphin conversion in primary cultures of rat cerebral cortex
- 1997
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In: Brain Research. - 0006-8993 .- 1872-6240. ; 760:1-2, s. 85-93
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Journal article (peer-reviewed)abstract
- Rat brain cortical cells in primary culture were used to investigate long-term effects of opiates on endopeptidases acting on dynorphin peptides. Enzyme activity in the soluble fraction of the cells converted dynorphin B to Leu-enkephalin-Arg6 and to a lesser extent to Leu-enkephalin. Five day treatment with 10 microM morphine increased the conversion to Leu-enkephalin-Arg6 by 370%. This effect was prevented by the presence of naloxone in the culture medium. The opiate-inducible activity was directed to the Arg-Arg bond in dynorphins with preference for dynorphin B > alpha-neoendorphin > > dynorphin A. The Km for the generation of Leu-enkephalin-Arg6 from dynorphin B was 40 microM. Enzyme activity was inhibited by dynorphin fragments, in the following order of potency: dynorphin A(1-13) > A(2-13) > A(1-17) > A(2-17) and by SH-reagents, suggesting the presence of a cysteine-protease. The opiate-stimulated dynorphin-converting enzyme (DCE)-activity affects the balance between dynorphin peptides (selective for kappa-opioid receptors) and enkephalin peptides (selective for delta-opioid receptors). Since both types of opioid peptides can influence the development of opiate tolerance, the change in the extent of this transformation may be functionally important.
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| 3. |
- Vlaskovska, Mila, et al.
(author)
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Opioid effects on 45Ca2+ uptake and glutamate release in rat cerebral cortex in primary culture
- 1997
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 68:2, s. 517-524
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Journal article (peer-reviewed)abstract
- Primary cultures of rat cortex, conveniently prepared from newborn animals, were used to study opioid effects on 45Ca2+ uptake and glutamate release. 45Ca2+ uptake, induced by treatment with glutamate or NMDA, was largely blocked by the NMDA antagonist MK-801. K+ depolarization-induced 45Ca2+ uptake was also reduced by MK-801, indicating that the effect was mediated by glutamate release. Direct analysis verified that glutamate, and aspartate, were indeed released. Opioid peptides of the prodynorphin system were also released and these, or other peptides, were functionally active, because naloxone treatment increased glutamate release, as well as the 45Ca2+ uptake induced by depolarization. Opioid agonists, selective for mu-, kappa-, and delta-receptors, inhibited the 45Ca2+ uptake induced by K+ depolarization. The combination of low concentrations of MK-801 and opioid agonists resulted in additive inhibition of K(+)-induced 45Ca2+ uptake. The results indicate that this system may be useful as an in vitro CNS model for studying modulation by opioids of glutamate release and Ca2+ uptake under acute, and perhaps also chronic, opiate treatment.
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