In another study on 6-hydroxydopamine (6-OHDA) model of PD in rats, the striatal tyrosine hydroxylase enzyme activity was restored with reversal of motor impairment, after a single intravenous administration of tyrosine hydroxylase-encoding plasmids and Tf receptor antibody conjugated PEGylated liposomes (Zhang et al., 2003). The gene discussed is TH; the disease is Parkinson disease.