Transcriptome profiling in 6-hydroxydopamine hemiparkinsonian rats reveals methamphetamine-mediated dopamine-independent changes in striatal gene expression

Unilateral injections of 6-hydroxydopamine into the medial forebrain bundle (MFB) is used extensively as a model of Parkinson’s disease. The present experiments examined whether a single injection of methamphetamine (METH) (2.5 mg/kg) could still influence striatal gene expression after 6-hydroxydopamine (DA)-induced destruction of the nigrostriatal dopaminergic pathway in the rat. Unilateral injections of 6-hydroxydopamine into the MFB resulted in total striatal dopamine depletion on the lesioned side. This injection also caused decreased striatal serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels. DA depletion was associated with increases in 5-HIAA/5-HT ratios which were potentiated by the METH injection. Microarray analyses revealed changes (+ 1.7-fold, p < 0.025) in the expression of 67 genes on the lesioned side in comparison to the intact side of the saline-treated hemiparkinsonian animals. These include follistatin, neuromedin U, and tachykinin 2 which were up-regulated. METH administration caused increases in the expression of several genes including c-fos, Egr1, and NOR-1 on the intact side. On the DA-depleted side, METH administration also increased the expression of 61 genes including Pdgfd and COX-2. There were METH-induced changes in 16 genes that were common in the DA-innervated and DA-depleted sides. These include c-fos and NOR-1 which show greater changes on the normal DA side. The present study documents METH-mediated DA-independent transcriptional alterations of several genes in the DA-denervated striatum. Our results also implicate serotonin as an important player in METH-induced gene expression because the METH injection also caused significant increases in 5-HIAA/5-HT ratios on the DA-depleted side. 31 samples. MNL (6), ML (6), SNL (5), SL (6), CS (4), CM (4)