Dopaminergic mRNA expression in the intact substantia nigra of unilaterally 6-OHDA-lesioned and grafted rats: an in situ hybridization study

The present study was performed to investigate the influence of intrastriat al fetal mesencephalic grafts on dopaminergic mRNA expression in the non-le sioned substantia nigra pars compacta of unilaterally 6-hydroxydopamine-les ioned rats. The expression of dopamine transporter mRNA, synaptic vesicular monoamine transporter mRNA and tyrosine hydroxylase mRNA was assessed in a djacent cryostat sections using in situ hybridization. Rotational behavior induced by apomorphine and amphetamine as well as hybridization of striatal sections cut at the grafting coordinates were used to prove the functional recovery and the presence of grafted cells, respectively. After grafting, the number of rotations was decreased and hybridization signals overlying c ells in the grafted striatum were detected. Mean grain densities overlying labeled neurons in the substantia nigra pars compacta of grafted rats were compared to those of shamgrafted rats and revealed differential expression of dopamine transporter mRNA, whereas synaptic vesicular monoamine transpor ter mRNA and tyrosine hydroxylase mRNA expression showed no difference. The results will be discussed in relation to previous in vitro and in vivo stu dies suggesting a reduction of functional dopamine transporter molecules in the contralateral striatum.