Non-opioid actions of opioid peptides
by
Wollemann M, Benyhe S.
Institute of Biochemistry,
Biological Research Centre,
Hungarian Academy of Sciences,
PO Box 521, H-6701 Szeged, Hungary.
Life Sci. 2004 Jun 4;75(3):257-70

ABSTRACT

Beside the well known actions of opioid peptides on micro-, delta- and kappa-opioid receptors, increasing amount of pharmacological and biochemical evidence has recently been published about non-opioid actions of various opioid peptides. These effects are not abolished by naloxone treatments. Such non-opioid effects are observed both in nervous tissues and in the cellular elements of the immune system. Peptides exhibiting non-opioid effects include beta-endorphin, dynorphin A, nociceptin/OFQ, endomorphins, hemorphins and a number of Proenkephalin A derived peptides, such as Met-enkephalin, Met-enkephalin-Arg-Phe (MERF) and bovine adrenal medullary peptide (BAM22). Non-opioid actions are exerted through different neuronal receptors, e.g., dynorphin hyperalgesia through NMDA receptor, Met-enkephalin induced regulation of cell growth through zeta (zeta) receptors, pain modulation by nociceptin through ORL-1 or NOP receptors, while BAM22 acts through sensory neuron specific G protein-coupled receptors (SNSR). We have investigated Met-enkephalin-Arg-Phe (MERF) and its analogues by the means of direct and indirect radioligand binding assays. It has been found that in addition to kappa(2) and delta-opioid receptors, MERF can act also through sigma(2)- or probably via FMRF-NH(2) receptors in rat cerebellum. A role of functionally assembling heterodimer receptors in mediating the non-conventional actions of these peptide ligands can not be excluded as well.

Babies
DALDA
Morphine
Tramadol
Why itch?
Nociceptin
Methadone
Endomorphins
P-glycoprotein
Morphine worms
Opiated crickets
Novelty and pain
Fentanyl and ketamine
Opioids, mood and cognition
Opioids, dopamine and alcohol
Opioids, goldfish and the giant toad
Heroin, cocaine and the squirrel monkey

Refs
and further reading

HOME
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The Abolitionist Project
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Critique of Huxley's Brave New World

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