Two different hSNCA-expressing control groups were used in this study, one that received AAV-hSNCA alone and one that received AAV-hSNCA and a control, non-silencing, silencing vector containing a scrambled sequence (AAV-NS), which interestingly differed in some of the toxic effects examined. Both hSNCA-expressing groups exhibited a similar forelimb motor deficit and similar loss of TH-IR neurons in the SN by 1 month. However, rats that received AAV-hSNCA and AAV-NS exhibited greater toxic effects than those observed in rats that received AAV-hSNCA alone, which included selleck chemicals loss of TH-IR

fibers in the ST, reduction in total TH expression in the ventral midbrain and the ST, as measured by western blot, and an increased inflammatory response as detected by Iba-1-IR. The greater toxicity observed in rats treated with AAV-hSNCA and AAV-NS could be attributed to silencing vector design, off-target effects of the scrambled sequence, Mitomycin C nmr or to increased

viral load. It is also possible that co-injection of silencing vector resulted in some unknown modulatory effect on hSNCA vector expression. Rats that received hSNCA alone did exhibit some reduction in total TH expression in the ventral midbrain and ST, as measured by western blot, although this reduction was not significant. A lack of toxicity on TH-IR fibers in the ST by AAV2/8-hSNCA alone, has also been observed in some studies where hSNCA was delivered to the SN using either AAV2/6 (Azeredo da Silveira et al., 2009) or AAV2/8 (McFarland et al., 2009). However, other studies using AAV2/2, 2/5 or 2/6 have shown hSNCA-induced reductions in TH-IR fibers in the ST by 8 weeks (Decressac et Progesterone al., 2012, Gorbatyuk et al., 2008, Kirik et al., 2002 and Lundblad

et al., 2012). These differences most likely reflect varying levels of hSNCA protein in DA axons due to differences in vector dose, serotype and/or efficiency of retrograde transport, but may also result from toxic effects at different ST levels since only one ST level was quantified. The AAV-hSNCA and AAV-NS group is the most appropriate hSNCA-expressing control group for assessment of effects due to hSNCA gene silencing with mir30-SNCA because both of these groups received similar viral load and were injected with similar vector constructs. When compared to the AAV-hSNCA and AAV-NS group, hSNCA gene silencing with mir30-SNCA results in significant protective effects on forelimb motor behavior, TH-IR neurons in the SN and TH-IR fibers in the ST. However, toxic effects that may have resulted from high viral load or from silencing vector design were observed in both the NS and mir30-SNCA groups.