Guinea-pigs treated with beta-endorphin fragments DTgammaE and DEgammaE exhibit reduced morphine inhibition of electrically-induced contractions.
The effect exerted by two gamma-endorphin derivatives (DTgammaE and DEgammaE) was investigated on morphine-induced inhibition on the electrically contractions of guinea pig ileum in vitro. Morphine (1x10(-8)-5x10(-8)-1x10(-7) M) dose dependently and significantly reduced the E.C. of guinea pig ileum, IC50=6.5x10(-8) M (Confidence limits: 3.7x10(-8)-9.1x10(-8)). DTgammaE and DEgammaEper se (1x10(-6)-5x10(-6)-1x10(-5) M) did not modify significantly the E.C. of guinea pig ileum. Furthermore, DTgammaE or DEgammaE injection 10-30-60 min before morphine, did not affect the inhibitory effect of morphine on the E.C. of guinea pig ileum. By contrast, ilea from guinea-pigs treated for 4 days with DTgammaE or DEgammaE (1 mg/Kg/i.p.) resulted less sensitive to the inhibitory effect of morphine, IC50=8.3x10(-7) M (Confidence limits: 1.4x10(-6)-3.5x10(-7)) for DTgammaE and IC50=7.7x10(-7) M (Confidence limits: 2.7x10(-6)-8.7x10(-7)) for DEgammaE. Our results indicate that chronic treatment of guinea pigs with DTgammaE or DEgammaE induces a significant reduction of the inhibitory effect of morphine on the E.C. of guinea-pig ileum thus confirming an important functional interaction between gamma-endorphin derivatives and opioid system.
Capasso
A
A
Dipartimento di Scienze Farmaceutiche, Università di Salerno, Italy. annacap@ponza.dia.unisa.it
Loizzo
A
A
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D004723:Endorphins / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009292:Narcotic Antagonists / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D013997:Time Factors; D001615:beta-Endorphin / Q000494:pharmacology*
D000701:Analgesics, Opioid; D004723:Endorphins; D009292:Narcotic Antagonists; D010446:Peptide Fragments; D001615:beta-Endorphin; C018903:gamma-endorphin, des-Tyr(1)-; C033558:des-enkephalin-gamma-endorphin; D009020:Morphine