dermorphin and Body-Weight

We studied delayed effects of sedatin (arginine-containing mu/delta-opioid receptor agonist) and its arginine-free analog on the ontogenetic development of fish. Fertilized eggs of the Amur sturgeon (Acipenser schrenckii) were treated with the peptides. The results indicate that sedatin increased activities of the antiradical and antioxidant defense systems, stimulated fry development by increasing body weight and length, and increased the number of nucleoli in the myocardium and liver of young fish.

Topics: Animals; Animals, Newborn; Body Size; Body Weight; Breeding; Female; Fishes; Heart; Larva; Liver; Male; Myocardium; Oligopeptides; Opioid Peptides; Receptors, Opioid, delta

1. The opioid activity of the amphibian peptide, [Lys7]dermorphin, was studied in rats and mice. When administered intracerebroventricularly (i.c.v.), intravenously (i.v.) or subcutaneously (s.c.) it produced a long lasting analgesia. Its antinociceptive potency exceeded that of morphine 290 times by i.c.v. injection, and 25-30 times by peripheral administration. 2. The dose-response curves of [Lys7]dermorphin antinociception were shifted to the right by the pretreatment with naloxone (0.1 mg kg-1, s.c.) or with the mu 1-selective antagonist, naloxonazine (10 mg kg-1, i.v. 24 h before peptide injection). 3. The peptide also displayed potent antinociceptive effects in a chronic inflammatory pain model (rat Freund's adjuvant arthritis). In this pain model, systemic administration of the peptide raised the nociceptive threshold more in inflamed than in healthy paw. 4. High central and peripheral doses of [Lys7]dermorphin in rats produced catalepsy. The cataleptic response was antagonized by naloxone but left unchanged by naloxonazine pretreatment. 5. In rats and mice, central or peripheral administration of [Lys7]dermorphin induced a significantly slower development of tolerance to the antinociceptive effect than did morphine. 6. Upon naloxone precipitation of the withdrawal syndrome, [Lys7]dermorphin-dependent mice made fewer jumps and lost less weight than the morphine-dependent animals. Withdrawal hyperalgesia did not develop in [Lys7]dermorphin-dependent mice. 7. In conclusion, [Lys7]dermorphin seems to be a unique opioid peptide having a high penetration into the blood-brain barrier despite its low lipid solubility. This peptide causes fewer side-effects than other opioids and appears less likely than morphine to cause physical dependence in rats and mice.

Topics: Analgesics, Opioid; Animals; Body Weight; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Tolerance; Male; Mice; Morphine; Naloxone; Nociceptors; Oligopeptides; Opioid Peptides; Rats; Rats, Wistar; Receptors, Opioid, mu; Substance-Related Disorders