Publications by authors named "Collin Merrill"

Article Synopsis
  • Tolerance to a substance requires increasing amounts of it over time to achieve the same effects, but the mechanisms behind this process are not fully understood.
  • Researchers are using Drosophila melanogaster (fruit flies) to study tolerance, as they share genetic similarities with humans that are relevant to alcohol responses and disorders.
  • The study reveals an inverse relationship between initial resistance to ethanol and tolerance development, suggesting that some mutants may display 'secondary' tolerance due to their initial sensitivity, and it proposes a new method for evaluating tolerance that takes this relationship into account.
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Article Synopsis
  • The brain has a vast diversity of cell types, and existing transgenic models often target multiple cell types rather than specific neurons.
  • An iterative ATAC approach was developed to enhance the specificity of transgene expression by identifying open chromatin regions in neurons, leading to more refined targeting of neuronal subsets.
  • This method not only helps in studying neurons linked to specific behaviors, like sleep, but is also versatile for use in other cell types and organisms.
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Article Synopsis
  • Tolerance requires increased substance amounts after initial exposure to achieve the same effects.
  • Researchers have studied model organisms, like fruit flies, to understand tolerance due to their relevance to human alcohol responses and overlapping genetic factors.
  • This study reveals an inverse relationship between initial resistance to alcohol and tolerance, suggesting that measuring tolerance should focus on relative change in sedation time, and offers a method to evaluate potential tolerance mutants using linear regression analysis.
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Article Synopsis
  • Gene regulation is essential for cellular function, with ATAC-seq emerging as a key method to study the epigenome and transcription mechanisms.
  • The study explored insulin signaling in Drosophila S2 cells, finding correlations between chromatin accessibility and gene expression changes.
  • The results indicate that insulin-induced chromatin modifications identified by ATAC-seq can be linked to specific enhancer regions that promote reporter gene expression.
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Article Synopsis
  • ATAC-seq is a technique that analyzes chromatin to study gene regulation, praised for its low input needs, quick process, and untargeted genome-wide insights.
  • While ATAC-seq is commonly applied to mammalian tissues, its application in Drosophila (fruit flies) is limited despite their favorable genetic tools for research.
  • The authors developed a tailored ATAC-seq workflow for Drosophila, optimizing steps for nuclei isolation and library construction, ultimately creating high-quality libraries for extensive chromatin research in these flies.
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Alcohol use disorder (AUD) exacts an immense toll on individuals, families, and society. Genetic factors determine up to 60% of an individual's risk of developing problematic alcohol habits. Effective AUD prevention and treatment requires knowledge of the genes that predispose people to alcoholism, play a role in alcohol responses, and/or contribute to the development of addiction.

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Objectives: URB937, a peripheral fatty acid amide hydrolase (FAAH) inhibitor, exerts profound analgesic effects in animal models. We examined, in rats, (1) the pharmacokinetic profile of oral URB937; (2) the compound's ability to elevate levels of the representative FAAH substrate, oleoylethanolamide (OEA); and (3) the compound's tolerability after oral administration.

Methods: We developed a liquid chromatography/tandem mass spectrometry (LC/MS-MS) method to measure URB937 and used a pre-existing LC/MS-MS assay to quantify OEA.

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Alcohol use is highly prevalent in the United States and across the world, and every year millions of people suffer from alcohol use disorders (AUDs). Although the genetic contribution to developing AUDs is estimated to be 50-60%, many of the underlying molecular mechanisms remain unclear. Previous studies from our laboratory revealed that lacking RhoGAP18B and Ras Suppressor 1 (Rsu1) display reduced sensitivity to ethanol-induced sedation.

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Changes in synaptic strength between hippocampal CA1 pyramidal cell synapses are partly responsible for memory acquisition. This plasticity is modulated by feedforward inhibitory interneurons in the stratum radiatum. While radiatum interneurons experience either long-term depression (LTD), short-term depression (STD), or lack plasticity, it is unclear whether plasticity correlates to specific interneuron subtypes.

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The hippocampus is thought to encode information by altering synaptic strength via synaptic plasticity. Some forms of synaptic plasticity are induced by lipid-based endocannabinoid signaling molecules that act on cannabinoid receptors (CB1). Endocannabinoids modulate synaptic plasticity of hippocampal pyramidal cells and stratum radiatum interneurons; however, the role of endocannabinoids in mediating synaptic plasticity of stratum oriens interneurons is unclear.

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A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

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Our understanding of the physiological and pathological functions of brain lipids is limited by the inability to analyze these molecules at cellular resolution. Here, we present a method that enables the detection of lipids in identified single neurons from live mammalian brains. Neuronal cell bodies are captured from perfused mouse brain slices by patch clamping, and lipids are analyzed using an optimized nanoflow liquid chromatography/mass spectrometry protocol.

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The endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG), a key modulator of synaptic transmission in mammalian brain, is produced in dendritic spines and then crosses the synaptic junction to depress neurotransmitter release. Here we report that 2-AG-dependent retrograde signaling also mediates an enduring enhancement of glutamate release, as assessed with independent tests, in the lateral perforant path (LPP), one of two cortical inputs to the granule cells of the dentate gyrus. Induction of this form of long-term potentiation (LTP) involved two types of glutamate receptors, changes in postsynaptic calcium, and the postsynaptic enzyme that synthesizes 2-AG.

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The ventral tegmental area (VTA) is involved in adaptive reward and motivation processing and is composed of dopamine (DA) and GABA neurons. Defining the elements regulating activity and synaptic plasticity of these cells is critical to understanding mechanisms of reward and addiction. While endocannabinoids (eCBs) that potentially contribute to addiction are known to be involved in synaptic plasticity mechanisms in the VTA, where they are produced is poorly understood.

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Transient receptor potential vanilloid 1 (TRPV1) was shown to modulate hippocampal CA1 pyramidal cell synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD). Synaptic plasticity is the cellular mechanism thought to mediate declarative learning and memory in the hippocampus. Although TRPV1 is involved in modulating hippocampal plasticity, it has yet to be determined how TRPV1 mediates its effects.

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Ventral tegmental area (VTA) GABA neurons appear to be critical substrates underlying the acute and chronic effects of ethanol on dopamine (DA) neurotransmission in the mesocorticolimbic system implicated in alcohol reward. The aim of this study was to examine the role of midbrain connexin-36 (Cx36) gap junctions (GJs) in ethanol intoxication and consumption. Using behavioral, molecular, and electrophysiological methods, we compared the effects of ethanol in mature Cx36 knockout (KO) mice and age-matched wild-type (WT) controls.

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