OBJECTIVE

To evaluate analgesic effect of N-phenylacetylglycyl-L-proline ethyl ester and cycloprolylglycine in formalin test in mice.

MATERIAL AND METHODS

Acute somatic pain in male ICR mice (n=48) was simulated by injecting 2.5% formalin into the hind paw. Throughout 30 min after injection, we recorded duration of pain reaction (paw raised above the floor of the chamber or tucked in; licking of the paw) in each phase: phase I (acute) (0-5 min); interphase (5-15 min); phase II (15-30 min). Analgesic effect of N-phenylacetylglycyl-L-proline ethyl ester and cycloprolylglycine was assessed after a single intraperitoneal injection 1 hour before testing at doses of 2 and 4 mg/kg.

RESULTS

N-phenylacetylglycyl-L-proline ethyl ester has the greatest analgesic effect at a dose of 2 mg/kg in interphase and phase II of formalin pain. Dose 4 mg/kg of dipeptide is effective only in interphase. Unlike its linear analogue, cycloprolylglycine 2 mg/kg reduces duration of pain reaction only in phase II.

CONCLUSION

N-phenylacetylglycyl-L-proline ethyl ester at doses 2 and 4 mg/kg has analgesic effect in formalin test in mice. This effect is superior to cycloprolylglycine in efficacy, time of onset and duration.