Discrete Cell Gene Profiling of Ventral Tegmental Dopamine Neurons after Acute and Chronic Cocaine Self-Administration

Abstract

Chronic cocaine administration induces a number of biochemical alterations within the mesolimbic dopamine system that may mediate various aspects of the addictive process such as sensitization, craving, withdrawal, and relapse. In the present study, rats were allowed to self-administer cocaine (0.5 mg/ infusion) for 1 or 20 days. Tyrosine hydroxylase immunopositive cells were microdissected from the ventral tegmental area (VTA) using laser capture microdissection, and changes in the abundances of 95 mRNAs were assessed using cDNA macroarrays. Five GABA-A receptor subunit mRNAs (␣4, ␣6, ␤2, ␥2, and ␦) were down-regulated at both 1 and 20 days of cocaine selfadministration. In contrast, the catalytic subunit of protein phosphatase 2A (PP2␣), GABA-A ␣1, and G␣ i2 were significantly increased at both time points. Additionally, calcium/ calmodulin-dependent protein kinase II␣ mRNA levels were increased initially followed by a slight decrease after 20 days, whereas neuronal nitric-oxide synthase mRNA levels were initially decreased but returned to near control levels by day 20. These results indicate that alterations of specific GABA-A receptor subtypes and other signal transduction transcripts seem to be specific neuroadaptations associated with cocaine selfadministration. Moreover, as subunit composition determines the functional properties of GABA-A receptors, the observed changes may indicate alterations in the excitability of dopamine transmission underlying long-term biochemical and behavioral effects of cocaine.

Cytosolic proteomic alterations in the nucleus accumbens of cocaine overdose victims

“…7,8,19 In addition to the cocaine-induced NAc plasticity, studies in rodent models indicate persistent or even permanent biochemical alterations in regions associated with the mesolimbic dopamine pathway including upregulation of the cyclic AMP (cAMP) pathway, [20][21][22][23][24][25][26] activator protein 1 family members [27][28][29][30][31][32] as well as glutamate, dopamine, gaminobutyric acid (GABA) and opiate receptors, growth factors, cytoskeletal elements and cell metabolism. [33][34][35][36][37][38][39][40][41] Genomic analyses in human post-mortem tissue of cocaine overdose (COD) victims have confirmed the findings of studies employing rodent models and have revealed novel mechanisms of drug-induced neuronal and non-neuronal dysregulation in human post-mortem brain tissue. [42][43][44][45] For example, Bannon and co-workers 42 examined gene expression in the NAc of post-mortem brain tissue of human cocaine abusers and controls and found significant alterations in several novel functional classes and transcripts including signal transduction, transcriptional and translational processing, neurotransmission and synaptic function, glia, structural and cell adhesion, receptors/transporters/ion channels, cell cycle and growth and lipid and protein processing.…”

Improved RNA preservation for immunolabeling and laser microdissection

“…Dysfunction or degeneration of these neurons leads to pathologies such as Parkinson's disease and addiction. A number of microdissection studies investigating molecular events in dopamine neurons have been carried out (Backes and Hemby 2003;Grimm et al 2004;Chung et al 2005;Greene et al 2005;Yao et al 2005;Cantuti-Castelvetri et al 2007;Stephenson et al 2007;Gründemann et al 2008;Lammel et al 2008). However, not all have immunolabeled to identify dopamine neurons.…”

In Vivo Ethanol Experience Increases D2 Autoinhibition in the Ventral Tegmental Area

“…Furthermore, repeated cocaine administration has been shown to cause upregulation of CaMKII expression in the VTA (Backes and Hemby, 2003;Licata et al, 2004). Therefore, differential regulation of the CaMKII-dependent desensitization mechanism may contribute to the difference in D 2 autoreceptor sensitivity, that is, increase vs decrease, following repeated intermittent administration of alcohol vs psychostimulants.…”