Withdrawal duration differentially affects c- fos expression in the medial prefrontal cortex and discrete subregions of the nucleus accumbens in cocaine-sensitized rats

• Published in: Neuroscience Vol. 114; no. 4; pp. 1061 - 1069
• Main Authors: Todtenkopf, M.S, Mihalakopoulos, A, Stellar, J.R
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2002; Elsevier
• Subjects: Animals; Biological and medical sciences; Cocaine - pharmacology; Cocaine-Related Disorders - physiopathology; core; dopamine; Dopamine - metabolism; Dopamine Uptake Inhibitors - pharmacology; Drug addictions; Genes, Immediate-Early - physiology; immediate early gene; Male; Medical sciences; mesocorticolimbic; Motor Activity - drug effects; Nucleus Accumbens - drug effects; Nucleus Accumbens - metabolism; Prefrontal Cortex - drug effects; Prefrontal Cortex - metabolism; Proto-Oncogene Proteins c-fos - biosynthesis; Rats; Rats, Sprague-Dawley; rostral pole; shell; Substance Withdrawal Syndrome - physiopathology; Toxicology; NAc SHELL, nucleus accumbens shell; PBTx, PB with 0.5% Triton-X 100; NAc RP, rostral pole of the nucleus accumbens; NMDA, N-methyl- D-aspartate; VTA, ventral tegmental area; NAc ARCH, arch of the nucleus accumbens shell; NAc CONE, cone of the nucleus accumbens shell; PL, prelimbic cortex; TH, tyrosine hydroxylase; mPFC, medial prefrontal cortex; ANOVA, analysis of variance; immediate early gene; ACCx, anterior cingulate cortex; DA, dopamine; NAc, nucleus accumbens; NAc LAT, lateral zone of the nucleus accumbens shell; IR, immunoreactive/immunoreactivity; FRA, Fos-related antigen; core; PB, phosphate buffer; rostral pole; mesocorticolimbic; IL, infralimbic cortex; shell; IEGs, immediate early genes; NAc CORE, nucleus accumbens core; NAc INT, intermediate zone of the nucleus accumbens shell; dopamine; NAc VERT, vertex of the nucleus accumbens shell; Rat; CNS stimulant; Psychotropic; Weaning; Rodentia; Central nervous system; Duration; Prefrontal cortex; Gene expression; Nucleus accumbens; Vertebrata; Mammalia; Animal; Cocaine; Drug of abuse; Protooncogene; Brain (vertebrata); Immediate early gene
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(02)00272-5

Intermittent administration of cocaine can result in behavioral sensitization, which is indicated by an augmented behavioral response to a subsequent administration of cocaine. This increase in behavior can be seen after various periods of abstinence from the drug, and is believed to model the cravings of drug users and the onset of drug addiction. It is believed that behavioral sensitization is mediated by activity of the mesocorticolimbic dopamine system. In particular, the nucleus accumbens and prefrontal cortex have been shown to play integral roles in this phenomenon. Recently, it has been demonstrated that the shell portion of the nucleus accumbens can no longer be considered a homogeneous structure, and can be subdivided into five separate regions. The present study was designed to assess the activation of key neuronal populations in subdivisions of the accumbens and subdivisions of the medial prefrontal cortex in cocaine-sensitized rats, using the expression of the immediate early gene, c- fos, as a marker of neuronal activation. Repeated cocaine administration resulted in robust sensitization that correlated with a significant decrease in the density of c- fos nuclei in all three subdivisions of the medial prefrontal cortex, and two subdivisions of the nucleus accumbens only in animals challenged after a 2-day withdrawal period. After a 2-week withdrawal period, sensitized animals no longer showed any differences in the density of c- fos nuclei in any of the areas examined, with the exception of a significant increase in the intermediate zone of the shell. The results indicate that distinct adaptations in neural activation take place in cocaine-sensitized rats that have been drug-free for various lengths of time. Furthermore, while specific subregions of brain areas known to play a role in drug abuse can be uniquely involved in the manifestations of cocaine sensitization, the functional roles of these subregions may differ depending on the time at which the behavior is assessed.