Detection of antisense PNA to the NTR1 (AS-NTR1) in brains of rats after i.p. injection of PNA. Animals received either saline or 10 mg/kg AS-NTR1 PNA (P1) i.p. Eight hours later these animals were perfused with sterile saline, and brains were harvested and flash-frozen. Brain extract was prepared as described in Methods. Standard curves were generated by using control brain extracts to which were added various concentrations of AS-NTR1 PNA. Lane 1, probe alone in Tris-EDTA buffer; lane 2, control brain + probe; lane 3, 10 mg/kg AS-NTR1 PNA treated animal at 8-hr post ip injection + probe. Lanes 4–8 contained control brain extract with probe and 0, 50, 100, 200, and 300 pg of PNA standard, respectively. The top arrow indicates the position of PNA/oligonucleotide probe hybrid, while the bottom arrow indicates the position of excess free oligonucleotide probe.