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Effects of miR-495 in Cocaine Addiction: Viral Mediated Overexpression and Inhibition of miR-495 Affects Cocaine-Seeking Behavior

Description

MicroRNAs are small, non-coding transcripts that control gene expression by preventing mRNA from translating into proteins. They have been implicated to play a role in many drug addictions. We previously

MicroRNAs are small, non-coding transcripts that control gene expression by preventing mRNA from translating into proteins. They have been implicated to play a role in many drug addictions. We previously found that miR-495 targets several addiction-related genes (ARGs) and is highly expressed in the nucleus accumbens (NAc). We also found miR-495 is downregulated in the NAc following acute cocaine administration, and cocaine motivation measured by breakpoint on a progressive ratio schedule of cocaine reinforcement is decreased when miR-495 is overexpressed. In this study, we manipulated the endogenous levels of miR-495 by using a viral vector. Using an animal model, rats were first trained for self-administration on a fixed ratio (FR) schedule of reinforcement. After they were infused with a lentivirus to overexpress (LV-miR-495) or decrease (LV-Sponge) miR-495, in the NAc shell. The rats were then tested for extinction and reinstatement of cocaine-seeking behavior, which are measures of motivation for cocaine. We measured the relative levels of miR-495 in the NAc shell using qRT-PCR. Our results show that overexpression of miR-495 decreased cocaine-seeking behavior during extinction and cocaine reinstatement, as we hypothesized. Surprisingly, miR-495 LV-sponge also decreased cocaine-seeking behavior in extinction, not as we hypothesized. However, we found that LV-Sponge failed to significantly decrease levels of miR-495 as intended. In conclusion, understanding why LV-Sponge decreased, rather than increased, miR-495 will need further study, however, the results with LV-miR-495 extend previous findings that miR-495 plays a vital role in the molecular mechanism that influences motivation to seek cocaine.

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Date Created
  • 2017-05

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Overexpression of MicroRNA-495 and its Effects on Cocaine Addiction

Description

Drug addiction is a pervasive problem in society, as it produces major increases in health care costs, crime, and loss of productivity. With over 3 million long-term users in America

Drug addiction is a pervasive problem in society, as it produces major increases in health care costs, crime, and loss of productivity. With over 3 million long-term users in America alone, cocaine is one of the most identifiable and addictive drugs. Cocaine produces major neurological changes in the central nervous system, including widespread changes in gene expression. MicroRNAs are small, non-coding transcripts that regulate gene expression post-transcriptionally by preventing translation into function protein. Given that one miRNA can target several genes simultaneously, they have the potential to attenuate drug-induced changes in gene expression. We previously found that the microRNA miR-495 regulates several addiction-related genes (ARGs) and is highly expressed in the nucleus accumbens (NAc), an important brain region involved in reward and motivation. Furthermore, acute cocaine decreases miR-495 expression and increases ARG expression in the NAc. Therefore, the aim of this thesis was to determine the effect of miR-495 overexpression in the NAc on cocaine self-administration behavior. Male Sprague Dawley rats were trained to lever press for cocaine and were then infused with a lentivirus into the NAc that either overexpressed green fluorescent protein (GFP, control) or miR-495+GFP. We then tested the rats on several doses of cocaine on both a fixed ratio (5) and progressive ratio (PR) schedule of reinforcement. We performed a follow-up experiment that included the same viral manipulation and testing, but the reinforcer was switched to food pellets. We found that NAc miR-495 overexpression reduces cocaine self-administration on a PR, but not an FR5, schedule of reinforcement. We found no effects of miR-495 overexpression on food reinforcement. These data suggest that NAc miR-495 regulates genes involved in motivation for cocaine, but not general motivation based on the data with food reinforcement. Future studies will seek to determine the specific target genes responsible for our behavioral effects.

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Date Created
  • 2016-05

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High-throughput identification of miRNA targets in the 3`UTRs of the soil nematode C. elegans

Description

miRNAs are short non-coding regulatory RNAs that have an important roles in a wide range of biological processes. Dysfunction of miRNA regulation has also been shown to occur in diseases

miRNAs are short non-coding regulatory RNAs that have an important roles in a wide range of biological processes. Dysfunction of miRNA regulation has also been shown to occur in diseases such as cancer. Despite the widespread influence of miRNAs in these contexts, the vast majority of miRNA targets are poorly characterized. The aim of this research project was to gain a better understating of miRNA targeting by using the model organism C. elegans. In order to do this I adapted a novel high-throughput assay to detect miRNA targets for use with the C. elegans 3`UTRome. As a proof of principle I performed this assay on 96 C. elegans 3`UTRs using high-throughput techniques. The results revealed miRNA interactions with two predicted 3`UTR targets for the miRNA lin-4 and ten unpredicted targets. The results also corroborated previous findings that certain worm miRNAs require special modifications to be expressed in human cells.

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Date Created
  • 2013-12