[D-Ala2,NMePhe4,Gly-ol5]enkephalin, but not [D-Pen2,L-Pen5]enkephalin, specifically inhibits behaviors induced by the dopamine D2 agonist RU 24213.
The effects of intracerebroventricular injection (10 microliters) of mu- and delta-selective opioid peptides on behaviors induced by the dopamine D2-selective agonist RU 24213 were investigated in the mouse, using multi-dimensional behavioral analyses. Fifteen to 30 min after the start of behavioral measurements, a 3.0 mg/kg dose of RU 24213 produced a marked increase in linear locomotion, circling, rearing and grooming behaviors. Although the mu-selective opioid peptide [D-Ala2,NMePhe4,Gly-ol5]enkephalin (DAGO) (0.003 and 0.01 microgram) itself did not significantly affect behaviors, DAGO (0.01 microgram) antagonized the RU 24213 (3.0 mg/kg)-induced increase in behaviors such as linear locomotion, circling, rearing, and grooming. Additionally, the effects of DAGO on RU 24213-induced behaviors were fully reversed by treatment with the mu-selective alkylating agent beta-funaltrexamine (beta-FNA) (5.0 micrograms). In contrast, the delta-selective opioid peptide [D-Pen2,L-Pen5]enkephalin (0.3 or 1.0 micrograms) had no marked effects on RU 24213 (3.0 mg/kg)-induced behaviors. These results suggest that mu- but not delta-opioid receptors play an inhibitory role in the behaviors induced by the selective activation of dopamine D2 receptors.
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Japan.
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Toyoshi
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Ukai
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Kameyama
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D015259:Dopamine Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D010627:Phenethylamines / Q000494:pharmacology*
D015259:Dopamine Agents; D004745:Enkephalins; D010627:Phenethylamines; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009271:Naltrexone; C016868:N-n-propyl-N-phenylethyl-4(3-hydroxyphenyl)ethylamine hydrochloride; C024524:beta-funaltrexamine; D020881:Enkephalin, D-Penicillamine (2,5)-