Abstract

EFFECTS OF NEWLY SYNTHESIZED ENDOMORPHIN-2 ANALOGS ON GUINEA PIG ILEUM

Kaloyan Georgiev*, Boris Kadinov and Tamara Pajpanova

Abstract

Endomorphin-1and endomorphin-2 are opioid tetrapeptides, which areisolated from bovine and human brain and have high affinity andselectivity to central μ-opioid receptors. In the digestive tract, opioidlikedrugs inhibit peristalsis and induce constipation. In this study, weanalyzed the effects of newly synthesized endomorphin-2 analogs –Deoxycholic-Tyr-Pro-Phe(pCl)-Phe-OH and Deoxycholic-Tyr-Pro-Phe(pF)-Phe-OH, on longitudinal muscle preparations from the guineapigileum (GPI). The both analogs used alone slightly affectspontaneous contractility of longitudinal muscle, but they significantlyreduce acetylcholine-induced contractility. The use of μ-opioidreceptor antagonist – naloxone increase the inhibitory effects onacetylcholine-stimulated contractility of GPI. Further research isnecessary to explain this interaction.

Keywords: endomorphin, nociception, ?-opioid receptor, deoxycholic acid, unnatural amino acids, naloxone.