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Linear and cyclic beta-casomorphin analogues with high analgesic activity
H L Rüthrich1, G Grecksch, R Schmidt
1Institute of Pharmacology and Toxicology, Medical Academy, Magdeburg, FRG.
Peptides
|May 1, 1992
Summary
Novel casomorphin (CM) derivatives exhibit potent analgesic effects, with cyclic [D-Orn2]CM-5 being over 1000 times more effective than morphine. These findings suggest delta and kappa receptors modulate nociception, not just mu receptors.
Area of Science:
- Pharmacology
- Neuroscience
- Medicinal Chemistry
Background:
- Casomorphins (CMs) are opioid peptides derived from casein.
- Understanding CM derivatives' antinociceptive properties is crucial for developing new analgesics.
Purpose of the Study:
- To investigate the antinociceptive efficacy of various casomorphin (CM) derivatives.
- To identify specific structural modifications that enhance analgesic potency.
Main Methods:
- Intraventricular administration of CM derivatives in male Wistar rats.
- Vocalization test to assess pain threshold changes post-injection.
- Analysis of analgesic effect at different time points (10-90 min).
Main Results:
- Cyclization and substitution with D-lysine or D-ornithine at position 2 significantly increased analgesic potency.
- Cyclic [D-Orn2]CM-5 and cyclic [D-Lys2]CM-5 demonstrated the highest antinociceptive activity.
- Cyclic [D-Orn2]CM-5 was over 1000 times more potent than morphine.
Conclusions:
- Specific structural modifications in CM derivatives lead to significantly enhanced analgesic effects.
- Mu receptor activity alone does not account for the observed analgesic activity.
- Delta and possibly kappa receptors play a role in modulating nociceptive effectiveness of CM derivatives.