CHRONIC intermittent exposure to psychomotor stimulants induces in the striatum the expression of Fos- related proteins (Fras) that persist after the end of drug treatment. We carried out experiments to determine whether such Fras (‘chronic Fras’) require dopamine D1-class receptor function for their persistent expression in the striatum. We chronically administered cocaine to rats in a behavioral sensitization protocol and blocked D1- class receptors with SCH23390 before a final cocaine challenge. Western blotting and immunohistochemical analyses indicate that Fras persistently expressed in response to chronic treatment include proteins of two types: those that have become independent of D1-class dopamine receptor activation and those that remain dependent on D1-class receptors for their expression following drug challenge.
1Department of Brain and Cognitive Sciences, MIT Building E25 Room 618, Cambridge, MA 02139
2Reproductive Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
3Hacettepe Universitesi Tip Fakultesi, Sihhiye, Ankara, Turkey
4Corresponding Author: Ann M. Graybiel
ACKNOWLEDGEMENTS: Supported by NIDA 5R01 DA08037. We thank Miss Diane Major for her help with the histology, Mr Glenn Holm, who made major contributions to the quantitative analysis, Mr Henry Hall, who is responsible for the photography-based chartings, and Drs M.I. Iadarola and R. Bravo for their generous gifts of antisera.
Received 12 August 1996; accepted 30 August 1996