title: Sensitized activation of Fos and brain-derived neurotrophic factor in the medial prefrontal cortex and ventral tegmental area accompanies behavioral sensitization to amphetamine.
abstract: Behavioral sensitization, or augmented locomotor response to successive drug exposures, results from neuroadaptive changes contributing to addiction. Both the medial prefrontal cortex (mPFC) and ventral tegmental area (VTA) influence behavioral sensitization and display increased immediate-early gene and BDNF expression after psychostimulant administration. Here we investigate whether mPFC neurons innervating the VTA exhibit altered Fos or BDNF expression during long-term sensitization to amphetamine. Male Sprague-Dawley rats underwent unilateral intra-VTA infusion of the retrograde tracer Fluorogold (FG), followed by 5 daily injections of either amphetamine (2.5 mg/kg, i.p.) or saline vehicle. Four weeks later, rats were challenged with amphetamine (1.0 mg/kg, i.p.) or saline (1.0 mL/kg, i.p.). Repeated amphetamine treatment produced locomotor sensitization upon drug challenge. Two hours later, rats were euthanized, and mPFC sections were double-immunolabeled for either Fos-FG or Fos-BDNF. Tissue from the VTA was also double-immunolabeled for Fos-BDNF. Amphetamine challenge increased Fos and BDNF expression in the mPFC regardless of prior drug experience, and further augmented mPFC BDNF expression in sensitized rats. Similarly, more Fos-FG and Fos-BDNF double-labeling was observed in the mPFC of sensitized rats compared to drug-naïve rats after amphetamine challenge. Repeated amphetamine treatment also increased VTA BDNF, while both acute and repeated amphetamine treatment increased Fos and Fos-BDNF co-labeling, an effect enhanced in sensitized rats. These findings point to a role of cortico-tegmental BDNF in long-term amphetamine sensitization.
authors.affiliation: Department of Pharmacology, Tufts University School of Medicine, Boston, MA, USA. fanoussa@mail.nih.gov
authors.forename: Sanya
authors.initials: S
authors.lastname: Fanous
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lacagnina
authors.forename: Ella M
authors.initials: EM
authors.lastname: Nikulina
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Hammer
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism* / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism* / Q000502:physiology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017557:Ventral Tegmental Area / Q000187:drug effects* / Q000378:metabolism
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D016760:Proto-Oncogene Proteins c-fos; D000661:Amphetamine