Effects of reversible inactivation of the ventral tegmental area on the acquisition and expression of morphine-induced conditioned place preference in the rat

The mesolimbic dopaminergic system that projects from the ventral tegmental area (VTA) to the nucleus accumbens is critical for initiation of opioid reinforcement and reward-related effects of drugs of abuse. In the present study, the effects of reversible inactivation of VTA on acquisition and expr...

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Bibliographic Details
Published in:Behavioural brain research 2009-03, Vol.198 (2), p.466-471
Main Authors: Moaddab, Mahsa, Haghparast, Abbas, Hassanpour-Ezatti, Majid
Format: Article
Language:English
Subjects:
Analgesics, Opioid - pharmacology
Anesthetics, Local - administration & dosage
Anesthetics, Local - toxicity
Animals
Behavioral psychophysiology
Biological and medical sciences
Conditioned place preference
Conditioning, Operant - drug effects
Dose-Response Relationship, Drug
Fundamental and applied biological sciences. Psychology
Injections, Subcutaneous
Lidocaine
Lidocaine - administration & dosage
Lidocaine - toxicity
Locomotor activity
Male
Microinjections
Morphine
Morphine - administration & dosage
Morphine - pharmacology
Motor Activity - drug effects
Psychology. Psychoanalysis. Psychiatry
Psychology. Psychophysiology
Rats
Rats, Wistar
Reinforcement (Psychology)
Reversible inactivation
Spatial Behavior - drug effects
Ventral tegmental area
Ventral Tegmental Area - drug effects
Ventral Tegmental Area - physiology
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Summary:The mesolimbic dopaminergic system that projects from the ventral tegmental area (VTA) to the nucleus accumbens is critical for initiation of opioid reinforcement and reward-related effects of drugs of abuse. In the present study, the effects of reversible inactivation of VTA on acquisition and expression of morphine-induced conditioned place preference (CPP) were investigated in rats. One hundred and eighty-one adult male albino Wistar rats were used in these experiments. Reversible inactivation of VTA was done through the unilateral and bilateral intra-VTA microinjection of 2% lidocaine during the acquisition and expression of morphine (5 mg/kg; s.c.)-induced CPP. Animal displacement, conditioning score and locomotor activity were recorded by Ethovision software. The results showed that bilateral but not unilateral intra-VTA administration of lidocaine significantly decreases the acquisition ( P < 0.01) and expression ( P < 0.05) of morphine-induced CPP compared to their respective saline-microinjected groups. Moreover, intra-VTA administration of lidocaine had no effect on locomotor activity in these experiments. Our results further support the idea that VTA may play an important role in the acquisition of morphine-induced CPP. In addition, there is no functional lateralization in the VTA for acquisition and/or expression of morphine-induced CPP in the rat.
ISSN:0166-4328
1872-7549
DOI:10.1016/j.bbr.2008.11.030