Different types of opioid receptors mediating analgesia induced by morphine, DAMGO, DPDPE, DADLE and beta-endorphin in mice.
The effects of intracerebroventricular (i.c.v.) administration of D-Phe-Cys-Tyr-D-Try-Orn-Thr-Pen-Thr-NH2 (CTOP), a selective mu-opioid receptor antagonist, (Allyl)2-Tyr-Aib-Aib-Phe-Leu-OH (ICI 174864) and (N,N-Bisallyl-Tyr-Gly-Gly-psi-(CH2S)-Phe-Leu-OH (ICI 154129), selective delta-opioid receptor antagonists on blocking analgesia induced by beta-endorphin, morphine, D-Ala2-NMePhe4-Gly-ol-enkephalin (DAMGO), D-Ala2-D-Leu5-enkephalin (DADLE) and D-Pen2-enkephalin (DPDPE) administered i.c.v. were studied in male ICR mice. The analgesia was assessed by the tail-flick and paw-licking (hot-plate) tests. The potencies of opioid agonists injected i.c.v. for producing analgesia were DAMGO greater than DADLE greater than beta-endorphin greater than morphine greater than DPDPE. Intracerebroventricular administration of CTOP (0.05 micrograms) selectively antagonized inhibition of the tail-flick and paw-licking response induced by morphine, DAMGO or DADLE but not beta-endorphin or DPDPE. ICI 174864 (5 micrograms) and ICI 154129 (5 micrograms) injected i.c.v. selectively antagonized analgesia induced by DPDPE or DADLE but not beta-endorphin, morphine or DAMGO injected i.c.v. These results indicate that analgesia induced by morphine and DAMGO is mediated by the stimulation of mu-opioid receptors while analgesia induced by DPDPE is mediated by the stimulation of delta-opioid receptors. DADLE-induced analgesia is mediated by the stimulation of both mu- and delta-opioid receptors. Analgesia induced by beta-endorphin is mediated by neither mu- nor delta-opioid receptors.
Suh
H H
HH
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226.
Tseng
L F
LF
D000698:Analgesia; D000818:Animals; D004723:Endorphins / Q000494:pharmacology*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D004745:Enkephalins / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects* / Q000502:physiology; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology; D001615:beta-Endorphin / Q000494:pharmacology
D004723:Endorphins; D004745:Enkephalins; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; D013004:Somatostatin; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; D016308:Enkephalin, Leucine-2-Alanine; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-; C040643:N,N-diallyl-tyrosyl-alpha-aminoisobutyric acid-phenylalanyl-leucine; C036405:ICI 154129