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A Gi2alpha antisense oligonucleotide differentiates morphine antinociception, constipation and acute dependence in
R B Raffa1, T L Goode, R P Martinez
1Drug Discovery Research, The R.W. Johnson Pharmaceutical Research Institute, Spring House, PA, USA.
Life Sciences
|January 1, 1996
Summary
Antisense oligodeoxyribonucleotide (oligo) targeting Gi2alpha G-protein subunits reduced morphine-induced pain relief but not dependence or constipation in mice. This suggests a specific pathway for antinociception, aiding drug discovery.
Area of Science:
- Neuroscience
- Pharmacology
- Molecular Biology
Background:
- Opioid analgesics like morphine are widely used for pain relief.
- Understanding the specific molecular pathways mediating opioid effects is crucial for developing safer and more effective analgesics.
- G-protein subunits play a significant role in cellular signaling, including responses to opioids.
Purpose of the Study:
- To investigate the role of specific G-protein subunits, particularly Gi2alpha, in mediating central morphine-induced antinociception.
- To differentiate the signaling pathways involved in morphine's analgesic effects from those involved in acute physical dependence and constipation.
Main Methods:
- Administration of antisense oligodeoxyribonucleotides (oligos) targeting different G-protein alpha subunits (Gi1alpha, Gi2alpha, Gi3alpha, G(s)alpha) intracerebroventricularly (i.c.v.) in mice.
- Assessment of morphine-induced antinociception using the tail-flick test.
- Evaluation of naloxone-precipitated jumping as a measure of acute physical dependence.
- Monitoring of morphine-induced constipation.
Main Results:
- Intracerebroventricular administration of antisense oligos against Gi2alpha significantly attenuated i.c.v. morphine-induced antinociception.
- Oligos targeting Gi1alpha, Gi3alpha, or G(s)alpha did not affect morphine-induced antinociception.
- None of the tested oligos altered naloxone-precipitated jumping (acute dependence) or morphine-induced constipation.
Conclusions:
- Central morphine-induced antinociception is preferentially mediated by a specific transduction pathway involving the Gi2alpha G-protein subunit.
- This pathway appears distinct from those mediating morphine-induced acute dependence and constipation.
- These findings offer novel opportunities for the development of analgesics with reduced side effects.