(+)-Morphine attenuates the (-)-morphine-produced conditioned place preference and the mu-opioid receptor-mediated dopamine increase in the posterior nucleus accumbens of the rat.

Full Abstract

An unbiased conditioned place preference paradigm and the microdialysis technique was used to evaluate the effect of (+)-morphine pretreatment on the conditioned place preference produced by (-)-morphine and the increased release of the dopamine produced by mu-opioid ligand endomorphin-1, respectively, in the posterior nucleus accumbens shell of the male CD rat. (-)-Morphine (2.5-10 microg) microinjected into the posterior nucleus accumbens shell dose-dependently produced the conditioned place preference. Pretreatment with (+)-morphine (0.1-10 pg) given into the posterior accumbens shell for 45 min dose-dependently attenuated the conditioned place preference produced by (-)-morphine (5 microg) given into the same posterior accumbens shell. However, higher doses of (+)-morphine (0.1 and 1 ng) were less effective in attenuating the (-)-morphine-produced conditioned place preference. Thus, like given systemically, (+)-morphine given into the posterior nucleus accumbens shell also induces a U-shaped dose-response curve for attenuating the (-)-morphine-produced conditioned place preference. Microinjection of mu-opioid agonist endomorphin-1 (1-10 microg) given into the ventral tegmental area dose-dependently increased the release of the extracellular dopamine in the posterior nucleus accumbens shell in the urethane-anesthetized rats. The increased dopamine caused by endomorphin-1 (10 microg) was completed blocked by the (+)-morphine (10 pg) pretreatment given into ventral tegmental area. It is concluded that (+)-morphine attenuates the (-)-morphine-produced conditioned place preference and the mu-opioid receptor-mediated increase of extracellular dopamine in the posterior nucleus accumbens shell of the rat.

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Author information

Author/s: Terashvili, Maia (M); Wu, Hsiang-En (HE); Schwasinger, Emma T (ET); Hung, Kuei-Chun (KC); Hong, Jau-Shyong (JS); Tseng, Leon F (LF);

Affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.

Grants: DA12588 (Agency:United States NIDA)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, N.I.H., Intramural; Research Support, Non-U.S. Gov't

Journal: European journal of pharmacology (Eur J Pharmacol), published in Netherlands. (Language: eng)

Reference: 2008-Jun; vol 587 (issue 1-3) : pp 147-54

Dates: Created 2008/06/02; Completed 2008/08/25;

PMID: 18448094, status: MEDLINE (last retrieval date: 11/6/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Analgesics, Opioid - antagonists & inhibitors; chemistry; pharmacology
Anesthesia
Animals
Chromatography, High Pressure Liquid
Conditioning, Operant - drug effects
Dopamine - metabolism
Dose-Response Relationship, Drug
Electrochemistry
Male
Microinjections

Microinjections
Morphine - antagonists & inhibitors; chemistry; pharmacology
Naloxone - pharmacology
Narcotic Antagonists - pharmacology
Nucleus Accumbens - anatomy & histology; drug effects; metabolism
Oligopeptides - administration & dosage; pharmacology
Rats
Receptors, Opioid, mu - drug effects
Stereoisomerism
Ventral Tegmental Area

Associated Chemicals: Analgesics, Opioid (0) ; Narcotic Antagonists (0) ; Oligopeptides (0) ; Receptors, Opioid, mu (0) ; endomorphin 1 (0) ; Naloxone (465-65-6) ; Dopamine (51-61-6) ; Morphine (57-27-2)

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