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The caffeine intake cause a local or wide ranges of convulsion and it is associated with release of dopamine (DA) receptors into the brain striatum. However, the effect of caffeine addiction on expression of DA receptors gene in the rat caudate-putamen (CPu), nucleus accumbens (NAc), and olfactory tubercle (OTu) has not been elucidated. In this study, we examined the influence of caffeine addiction on DA D ₁and D₂receptor mRNAs after the treatment of caffeine for four weeks. Using the specific antisense ribo-probes for DA D₁and D₂receptor cDNAs, in situ hybridization was performed on the CPu, NAc, and OTu of the adult male Sprague Dawely rats. In caffeine-treated group, DA D₁and D₂receptor mRNAs were highly increased in CPu, NAc, and OTu. The expression density of DA D₁receptor mRNAs were 2.52±1.40 (CPu), 2.78±1.69 (NAc), and 3.91±1.28 (OTu) in control group and 7.76±2.09 (CPu), 4.2 ±1.85 (NAc), and 8.21±1.72 (OTu) in caffeine-treated group. The expression density of DA D₂receptor mRNA was 2.32±1.52 (CPu), 2.63±2.11 (NAc), and 3.61±1.43 (OTu) in control group, and 6.41±1.82 (CPu), 6.89±1.32 (NAc), and 6.82±1.18 (OTu) in caffeine-treated group. DA D₁receptor mRNA was higher expressed than DA D₂ receptor mRNA in CPu and NAc. These results suggest that caffeine reacts as a upregulator of the expression of DA D₁and D₂receptor mRNA among the neurotransmitters.
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