Abstract: The present invention is directed to small interfering RNAs that down regulate expression of a synuclein gene and methods of using the small interfering RNAs.

Abstract: A vector and a method are provided for delivering a nucleic acid to a nervous system cell. The vector includes a first nucleic acid, a second nucleic acid, inverted terminal repeats of adeno-associated virus, and a tetracycline-off regulatable promoter system that includes a first promoter operably linked to the first nucleic acid and a second promoter operably linked to the second nucleic acid. The promoters drive expression in opposite directions and away from the inverted terminal repeats. The method includes providing a recombinant adeno-associated viral (rAAV) vector and administering the vector to a nervous system cell. Expression of a product from the first nucleic acid is regulatable by the promoter system.