Locomotor sensitization to cocaine is associated with increased Fos expression in the accumbens, but not in the caudate

Behav Brain Res. 2002 Nov 15;136(2):455-62. doi: 10.1016/s0166-4328(02)00196-1.


Behavioral sensitization following repeated intermittent cocaine administrations is thought to involve alterations in cocaine regulation of neural activity within the accumbens and caudate brain regions. Although Fos immunohistochemistry and c-fos in situ hybridization have frequently been used to assess changes in cocaine-induced neural activity following prior cocaine exposure, these techniques have rarely been used to examine neural activity in the accumbens of behaviorally sensitized animals. In the present experiment, we compared the ability of increasing doses of cocaine to induce Fos in the accumbens and caudate of rats following a treatment procedure (7 once daily injections of 15 mg/kg of cocaine or the saline vehicle) shown to produce robust and persistent (1 week) locomotor sensitization. In sensitized animals, there was a leftward shift in the dose-response curve for cocaine induction of Fos in the accumbens, but not in the caudate. These results provide the first parametric evidence for sensitization of cocaine-induced Fos expression in the accumbens.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Caudate Nucleus / drug effects
  • Caudate Nucleus / metabolism*
  • Cell Nucleus / metabolism
  • Cocaine / pharmacology*
  • Dose-Response Relationship, Drug
  • Gene Expression / drug effects*
  • Genes, fos / drug effects*
  • Immunohistochemistry
  • Male
  • Motor Activity / drug effects*
  • Nucleus Accumbens / drug effects
  • Nucleus Accumbens / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Stimulation, Chemical


  • Cocaine