A recombinant adenoviral tetracycline-regulated system with neuron-specific enolase (NSE) promoter was injected stereotaxically into the striatum of rat brains. The efficiency of in vivo transfection was quantified by counting the number of green fluorescent protein (GFP)-positive cells at 3 days, 1 week, and 4 weeks after injection. NeuN immunohistochemistry demonstrated that expression of gammaPKC-GFP was dominant (20-99%) in neuron and expression of gammaPKC-GFP in neuron was significantly higher in pups than adult rats. These results indicate that tetracycline-inhibitable transcription factor (tTA) can drive tetracycline-responsive promoter (TetOp) under the control of NSE promoter, thereby efficiently and selectively expressing gammaPKC-GFP in neurons in vivo. (C) 2004 Elsevier Inc. All rights reserved.