Basal and cocaine-induced opioid receptor gene expression in the rat CNS analyzed by competitive reverse transcription PCR.
The basal mRNA levels of kappa and mu opioid receptors, as well as their regulation after 'binge' cocaine administration, were determined with competitive reverse transcription polymerase chain reaction (RT-PCR) in brain regions of male Sprague-Dawley rats. The procedure proved to be a reliable method to quantify the relative opioid receptor gene expression. The highest basal mRNA levels for the kappa opioid receptor were found in the nucleus accumbens and hypothalamus, whereas the highest basal mRNA expression for the mu opioid receptor was observed in the hypothalamus. Rats were separately treated with 'binge' (three hourly injections) cocaine HCl (45 mg/kg/day i.p.) or saline (1 ml/kg i.p.) for 2 days. A significant down-regulation of the kappa opioid receptor mRNA was detected in the nucleus accumbens. The mu opioid receptor mRNA was not affected. The data suggest a selective effect on kappa receptor expression in the nucleus accumbens as a consequence of 'binge' cocaine use.
Department of Clinical Neuroscience, Experimental Drug Addiction Research Section, Karolinska Institutet, CMM L8: 01, S-171 76, Stockholm, Sweden. asa.rosin@cmm.ki.se
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Rosin
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van der Ploeg
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Georgieva
D000818:Animals; D002490:Central Nervous System / Q000187:drug effects* / Q000378:metabolism; D003042:Cocaine / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects*; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D009714:Nucleus Accumbens / Q000378:metabolism; D009928:Organ Specificity; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000235:genetics* / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D012333:RNA, Messenger; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D003042:Cocaine