title: Overexpression of BDNF in the ventral tegmental area enhances binge cocaine self-administration in rats exposed to repeated social defeat.
abstract: Stress is a major risk factor for substance abuse. Intermittent social defeat stress increases drug self-administration (SA) and elevates brain-derived neurotrophic factor (BDNF) expression in the ventral tegmental area (VTA) in rats. Intra-VTA BDNF overexpression enhances social defeat stress-induced cross-sensitization to psychostimulants and induces nucleus accumbens (NAc) ΔFosB expression. Therefore, increased VTA BDNF may mimic or augment the development of drug abuse-related behavior following social stress. To test this hypothesis, adeno-associated virus (AAV) was infused into the VTA to overexpress either GFP alone (control) or GFP + BDNF. Rats were then either handled or exposed to intermittent social defeat stress before beginning cocaine SA training. The SA acquisition and maintenance phases were followed by testing on a progressive ratio (PR) schedule of cocaine reinforcement, and then during a 12-h access "binge" cocaine SA session. BDNF and ΔFosB were quantified postmortem in regions of the mesocorticolimbic circuitry using immunohistochemistry. Social defeat stress increased cocaine intake on a PR schedule, regardless of virus treatment. While stress alone increased intake during the 12-h binge session, socially-defeated rats that received VTA BDNF overexpression exhibited even greater cocaine intake compared to the GFP-stressed group. However, VTA BDNF overexpression alone did not alter binge intake. BDNF expression in the VTA was also positively correlated with total cocaine intake during binge session. VTA BDNF overexpression increased ΔFosB expression in the NAc, but not in the dorsal striatum. Here we demonstrate that VTA BDNF overexpression increases long-access cocaine intake, but only under stressful conditions. Therefore, enhanced VTA-BDNF expression may be a facilitator for stress-induced increases in drug abuse-related behavior specifically under conditions that capture compulsive-like drug intake.
authors.affiliation: University of Arizona College of Medicine, Phoenix, AZ.|School of Life Sciences, Arizona State University, Tempe, AZ.
authors.forename: Junshi
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Bastle
authors.affiliation: School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY.
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Bass
authors.affiliation: University of Arizona College of Medicine, Phoenix, AZ.|School of Life Sciences, Arizona State University, Tempe, AZ.
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Hammer
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ.
authors.forename: Janet L
authors.initials: JL
authors.lastname: Neisewander
authors.affiliation: University of Arizona College of Medicine, Phoenix, AZ.
authors.forename: Ella M
authors.initials: EM
authors.lastname: Nikulina
mesh_terms: D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis* / Q000235:genetics; D003042:Cocaine / Q000008:administration & dosage*; D005260:Female; D015870:Gene Expression; D057967:Infusions, Intraventricular; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D012646:Self Administration; D012919:Social Behavior; D013315:Stress, Psychological / Q000378:metabolism* / Q000523:psychology; D017557:Ventral Tegmental Area / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D003042:Cocaine
keywords: Brain-derived neurotrophic factor; Cocaine self-administration; Nucleus accumbens; Social defeat stress; deltaFosB