EXOGENOUS ATYPICAL OPIOID PEPTIDES INHIBIT HYPERALGESIA ASSOCIATED WITH CARRAGEENAN PERIPHERAL INFLAMMATION.

Jaba, Irina M.; Tamba, B.; Albu, Elena; Leon, Magdalena; Mungiu, O. C.

Studies examining the role of the endogenous opioid system in modulating edema and hyperalgesia in animal models of inflammatory pain are contradictory. The present study investigates whether exogenous atypical opioid peptides contribute to the modulation of localized inflammatory nociception. Inflammation was induced by intraplantar injection of carrageenan into the right hindpaw. Mechanical and thermal thresholds were determined respectively in order to determine the potential of the tested peptides in inhibiting hyperalgesia during inflammation. The evolution of the edema was monitored using a plethysmometer. Delta opioid agonist ([D-Ala2]deltorphin II) and miu opioid agonist 1-3 beta casomorphin were administered peripherally into the right hind paw. The exogenous opioid peptides tested induced a signifficant antihyperalgesic effect. The peptides were antihyperalgesic without significantly affecting edema, indicating that peripheral opioid receptors are not involved in edema formation due to acute inflammation. These results demonstrate the peripheral analgesic potential of atypical opioid peptides such as casomorphins and deltorphins. The differential effects of on mechanical versus thermal thresholds support the notion that distinct neuroanatomical or neurochemical mechanisms modulate the processing of thermal versus mechanical stimuli.

HYPERALGESIA; ANIMAL models of inflammation; OPIOID peptides; EDEMA; CARRAGEENANS; ANTI-inflammatory agents

Therapeutics, Pharmacology & Clinical Toxicology, 2011, Vol 15, Issue 4, p285

1583-0012

Academic Journal