Long-term suppression of methamphetamine-induced c-Fos expression in rat striatum by the injection of c-fos antisense oligodeoxynucleotides absorbed in water-absorbent polymer.

The use of water-absorbent polymer (WAP) as a hydrogel carrier for the slow delivery of antisense oligodeoxynucleotides (ODN) in the brain, was recently developed. In this experiment, 15-mer phosphorothioate ODN, complementary to c-fos gene absorbed in WAP, was injected in the rat striatum. The expression of c-Fos-immunoreactivity induced by methamphetamine (6 mg/kg, intraperitoneally) around the injection site was suppressed until 5 days after injection. Using this method, it was observed that unilateral injection with c-fos antisense ODN into the rat striatum caused robust ipsilateral rotations after methamphetamine challenge 4 days post injection. This method is simple, and the biological and behavioral effects of antisense ODN in WAP can be maintained for several days even after a single injection into the brain.