It should be noted that whole striata were taken for our analyses to avoid sampling errors from individual punch collections. We define such results as “gross striatal values”. Concerns may be raised regarding the use of entire striata taken for ELISA since, potentially, the readouts might have underestimated the levels of exogenously expressed GDNF. Our data from individual punch collections indicated more wide-ranging values with the lower mean than for the data generated from the entire striata. This confirmed and validated the usage of whole striata for ELISA rather than single tissue snips. “Gross striata values” assure that the entire injected structure is taken into consideration with more precise quantification of GDNF expression. One of the disadvantages of the two-vector system is also the need to co-transduce neurons with both vectors for regulation to occur. The method of co-transduction with two separate AAV vectors compensates for the restrictions concerning gene insertion into the small AAV vectors. The AAV cotransfection may raise concerns regarding efficiency of transgene SCH772984 942183-80-4 expression from two mixed AAV vectors and injected into a single site. Fan et al. showed that the tyrosine hydroxylase gene and also the aromatic L-amino acid decarboxylase gene were simultaneously transduced into rat striatal cells via two separate AAV vectors, AAV-TH and AAV-AADC. Immunostaining showed that TH and AADC were co-expressed efficiently in the same striatal cells in vitro and in vivo. Moreover, co-transduction with these two vectors resulted in more effective dopamine production and more remarkable behavioral recovery in 6-hydroxydopamine -lesioned rats, compared with rats receiving AAV-TH alone. Later, the same group tried a triple transduction with AAV’s expressing TH, AADC, and GTP Cyclohydrolase I. Similarly to their previous results, triple transduction resulted in greater dopamine production in denervated striatum of parkinsonian rats. Molecular studies by Yang et. al have demonstrated that intermolecular recombination between monomer circular intermediates is, at least in part, responsible for the formation of AAV circular concatamers associated with long-term episomal persistence and transgene expression. New single-vector systems that can accommodate both the regulatory components and the transgene, eliminating the need for co-transduction have already been designed. It should also be emphasized that, for clinical applications, precise targeting and distribution of the vector is warranted. Real-time convective delivery of gene therapy vectors has been proposed to address this need. A similar dual-component AAV2-regAADC vector system has also been tested in rat brain. Induction of Aromatic L-Amino Acid Decarboxylase expression has been shown in the striatum of unilaterally 6-OHDA-lesioned rats by i.p. injection of rapamycin. Induction of AADC in the lesioned striatum was associated with the development of L-dopa-induced turning behavior.