When examined across the 5–30 days after viral infusion, a decrease in active lever responding was observed beginning 12 days after infusion of the Ad-shα4 virus, reaching a maximum 18–19 days after infusion (Fig. 1d), and returning to baseline levels ~23 days after virus infusion. We have found that shRNAs expressed by the adenovirus also reduce target mRNAs over a similar time period, suggesting that the transient suppression of target gene expression is responsible for the transient behavioral effects (Jeanblanc et al. 2009; Rewal et al. 2009). It should be mentioned that a subset of rats (n = 8) received a weekend (two sessions) off between day 22 and day 23, presumably accounting for the rather abrupt recovery of behavior in Fig. 1d and e.
