No abstract

Chronic cocaine abuse induces long-term neural adaptations as a consequence of alterations in gene expression. This study was undertaken to identify those transcripts differentially regulated in the nucleus accumbens of human cocaine abusers. Affymetrix microarrays were used to measure transcript abundance in 10 cocaine abusers and 10 control subjects matched for age, race, sex, and brain pH. As expected, gene expression of cocaine-and amphetamine-regulated transcript (CART) was increased in the nucleus accumbens of cocaine abusers. The most robust and consistent finding, however, was a decrease in the expression of a number of myelin-related genes, including myelin basic protein (MBP), proteolipid protein (PLP), and myelin-associated oligodendrocyte basic protein (MOBP). The differential expression seen by microarray for CART as well as MBP, MOBP, and PLP was verified by RT-PCR. In addition, immunohistochemical experiments revealed a decrease in the number of MBP-immunoreactive oligodendrocytes present in the nucleus accumbens and surrounding white matter of cocaine abusers. These findings suggest a dysregulation of myelin in human cocaine abusers. Keywords: cocaine, human, microarray, myelin basic protein, nucleus accumbens, post-mortem. Drug addiction, which constitutes a serious threat to public health, is a multifaceted disorder involving tolerance, dependence, craving, and relapse (Nestler 2002). A better understanding of the molecular mechanisms underlying drug addiction would presumably facilitate the development of more successful treatment strategies. Although the molecular basis of drug abuse is not fully understood, more is known about the neural systems subserving this disorder. In particular, animal studies have identified the nucleus accumbens as a brain region that plays a critical role in addiction (Dackis and O'Brien 2001;Everitt and Wolf 2002). Furthermore, in animal models, chronic exposure to cocaine induces structural and functional changes in the nucleus accumbens that are presumably mediated by altered gene expression (Toda et al. 2002;Norrholm et al. 2003).Although animal models continue to advance our understanding of the neurobiological underpinnings of drug abuse, it is difficult to model some uniquely human aspects of cocaine abuse, namely the spontaneous self-administration of cocaine, most often in a binging pattern of abuse, over a period of years or decades. Analysis of post-mortem brain provides a unique opportunity to examine changes in gene expression in the human drug abuser (Hurd and Herkenham 1993;Segal et al. 1997;Bannon et al. 2002). Recently, microarray technology has been employed to analyze gene expression in complex brain disorders (Mirnics et al. 2001). In the present study, we used DNA microarrays to investigate changes in gene expression in the nucleus accumbens of chronic cocaine abusers relative to carefully matched control subjects. Received September 8, 2003; revised manuscript received October 30, 2003; accepted October 31, 2003. Address corresponde...

The tachykinins comprise a family of closely related peptides that participate in the regulation of diverse biological processes. The tachykinin peptides substance P, neurokinin A, neurokinin A(3-10), neuropeptide K, and neuropeptide gamma are produced from a single preprotachykinin gene as a result of differential RNA splicing and differential posttranslational processing. Another tachykinin, neurokinin B, is produced from a separate preprotachykinin gene. These preprotachykinin mRNAs and peptide products are differentially distributed throughout the nervous system. Three distinct G protein-coupled tachykinin receptors exist for these tachykinin peptides. The three receptors interact differentially with the tachykinin peptides and are uniquely distributed throughout the nervous system. The NK-1 receptor preferentially interacts with substance P, the NK-2 receptor prefers neurokinin A, neuropeptide K, and neuropeptide gamma, and the NK-3 receptor interacts best with neurokinin B. Examples of the roles of tachykinin peptidergic neuronal systems are taken from the spinal cord sensory system and the nigrostriatal extrapyramidal motor system. Analysis of the functional significance of multiple tachykinin peptide systems, receptor-second messenger coupling mechanisms, and developmental and regulatory mechanisms underlying peptide mRNA and receptor expression represent areas of current and future investigation.

The importance of the nuclear receptor nurr1 for the appropriate development of mesencephalic dopaminesynthesizing neurons has been clearly demonstrated through the targeted disruption of the nurr1 gene. The persistence of nurr1 expression in adult tissue suggests a possible role for this transcription factor in the maintenance, as well as development, of the dopaminergic phenotype. To address this issue, we analyzed the effects of nurr1 on the transcriptional expression of the human dopamine transporter gene (hDAT), one of the most speci®c phenotypic markers for dopaminergic neurons. Nurr1 enhanced the transcriptional activity of hDAT gene constructs transiently transfected into a newly described cell line (SN4741) that expresses a dopaminergic phenotype, whereas other members of the NGFI-B subfamily of nuclear receptors had lesser or no effects. Nurr1 activation of hDAT was not dependent upon heterodimerization with the retinoid X receptor. Unexpectedly, functional analysis of a series of gene constructs revealed that a region of the hDAT 5 H -¯anking sequence devoid of NGFI-B response element (NBRE)-like sites mediated nurr1 activation. Additional experiments using a nurr1 mutant construct suggest that nurr1 activates hDAT transcription via a novel NBRE-independent mechanism.