Centrally administered beta-endorphin produces prolonged changes in delta-opioid ligand activity in vivo.
Spontaneous reflex bladder contractions were recorded isometrically in urethane anesthetized rats. Bladder contractions were depressed by intracerebroventricular injections of the mu-opioid receptor agonist [D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAGO) and the delta-agonist [2D-penicillamine,5D-penicillamine]enkephalin (DPDPE) respectively. The effect of DPDPE was selectively antagonized by ICI 174,864 (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH; Aib = alpha-aminoisobutyric acid). However following the administration of beta-endorphin the antagonistic action of ICI 174,864 could no longer be observed. In addition ICI 174,864 exhibited agonistic activity following beta-endorphin and the effects of DPDPE were prolonged in a dose related manner by beta-endorphin. These observations suggest that beta-endorphin may produce complex changes in central delta-opioid receptor activity.
D000818:Animals; D004723:Endorphins / Q000008:administration & dosage / Q000494:pharmacology*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D007276:Injections, Intraventricular; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects*; D017465:Receptors, Opioid, delta; D001743:Urinary Bladder / Q000187:drug effects; D001615:beta-Endorphin
D004723:Endorphins; D004745:Enkephalins; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; D020881:Enkephalin, D-Penicillamine (2,5)-; C040643:N,N-diallyl-tyrosyl-alpha-aminoisobutyric acid-phenylalanyl-leucine