The intrastriatal infusions of 'naked' small interfering RNA (siRNA) targeted to dopamine D1 receptors (1.0-10.0 nmol over 3 days) did not reduce dopamine D1 receptor messenger RNA levels or receptor protein, assessed by [125I] SCH 23982 binding in intact rats. This was in contrast to results in vitro where a 76% reduction in dopamine D1 receptor ligand binding could be observed.
Conclusion: The results suggest that synthetic siRNA, when applied directly to rat brain, is not capable of inducing RNA interference.