1992 — 2007 |
Brodie, Mark S |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Ethanol-Neurotransmitter Interactions in Brain Neurons @ University of Illinois At Chicago
The overall objective of these studies is to understand how ethanol acts on brain areas involved in the mediation of reward, and to determine how specific neurotransmitter systems modify the action of ethanol on brain reward pathways. This knowledge might be exploited to develop drugs which reduce alcohol craving, leading to effective treatments for alcohol abuse. Recent studies have shown that serotonin (5-HT) reuptake inhibitors decrease alcohol abuse in problem drinkers. Although the reason for this is not clear, it is possible that 5-HT reuptake inhibitors act in brain areas involved in reward to reduce alcohol craving. One brain area shown to be important for mediating the rewarding effects of many drugs of abuse is the ventral tegmental area of Tsai (VTA). The VTA is the source of dopaminergic innervation to a number of brain areas (e.g., the nucleus accumbens and the prefrontal cortex) thought to be involved in the rewarding effects of drugs of abuse, and dopamine is an important neurotransmitter in reward. Intracellular and extracellular recording in rat brain slices will be used to assess the action of ethanol and 5-HT on dopaminergic neurons in the VTA. Slices (400 micromoles thick) will be mounted and totally submerged in the recording chamber. Ethanol will be applied in known concentrations in the bath. Ethanol, in concentrations within the behaviorally active range, causes excitation of dopaminergic VTA neurons. Our preliminary data indicates that 5-HT potentiates the excitatory effect of ethanol on some of these VTA neurons. The electrophysiological effects of 5-HT on dopamine-containing neurons of the VTA will be characterized in order to elucidate the mechanism by which 5-HT enhances ethanol-induced excitation in these neurons. Furthermore, the specific 5-HT receptor subtype(s) which mediate this potentiation will be identified. 5-HT reuptake blockers will be examined to determine if they also potentiate the effects of ethanol on VTA neurons, and whether potentiation by these agents is due to their action at serotonergic synapses. In addition, inbred strains of rats (Lewis and Fisher 344) which differ in voluntary EtOH intake will be used to determine whether the sensitivity of VTA neurons to 5-HT potentiation of EtOH excitation is correlated with a genetic predisposition to drink more or less EtOH. Ultimately, these studies may provide a rationale for the efficacy of 5-HT reuptake inhibitors in reducing alcohol abuse, and might also provide a basis for the development of more selective 5-HT-related drugs which would be useful in the treatment of uncontrolled ethanol intake.
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1994 — 2000 |
Brodie, Mark S |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Ethanol/Neurotransmitter Interactions in Brain Neurons @ University of Illinois At Chicago
The overall objective of this project is to understand how ethanol acts on brain areas involved in the mediation of reward, and to determine how specific neurotransmitter systems modify the action of ethanol on brain reward pathways. Drugs acting on the serotonergic system reduce voluntary ethanol intake in laboratory animals and in clinical studies. These drugs may act at brain areas involved in reward to reduce alcohol craving. The ventral tegmental areas of Tsai (VTA) is important for mediating the rewarding properties of many drugs of abuse, including ethanol. Whole cell patch recording from acutely dissociated dopaminergic VTA neurons will be used to assess the action of ethanol and serotonin on these cells. Drugs will be applied in known concentrations. Ethanol causes excitation of most VTA neurons in extracellular and intracellular studies. We have shown that serotonin potentiates the excitatory effect of ethanol on VTA neurons, and this effect is mediated by 5-HT/2 receptors. We will investigate changes in specific membrane currents which may underlies serotonin potentiation of ethanol effects. Specific Aim #1 is to investigate the effects of serotonin and ethanol on potassium currents which mediate the after hyperpolarization following spontaneous action potentials. The specific currents which we intend to examine include two calcium-dependent potassium conductances, SK and BK, A-current (I/A), and the delayed rectifier. Specific Aim #2 is to determine how M-current, which is reduced by serotonin in other preparations, is affected by ethanol, serotonin and by the combination of ethanol and serotonin, in VT neurons. Specific Aim #3 is to determine whether serotonin alters h-current (I/h), a hyperpolarization-activated inward rectifier current, and to determine whether the effect of ethanol to enhance I/h is increased in the presence of serotonin. From the results of these experiments, a model will be developed to describe the interactions between the effects of serotonin and ethanol which result in potentiation of ethanol-induced excitation. These studies should elucidate the ionic mechanisms by which serotonin alters the action of ethanol in the VTA. This knowledge could be exploited to develop drugs for the treatment of alcoholism which reduce ethanol craving.
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2009 — 2011 |
Brodie, Mark S |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Intracellular Study of Ethanol Effects On Brain Neurons @ University of Illinois At Chicago
Dopaminergic (DA) neurons in the ventral tegmental area (VTA) provide the DA innervation of the nucleus accumbens;this mesolimbic DA pathway is important for the rewarding properties of ethanol. Ethanol directly excites acutely dissociated DA VTA neurons, in the absence of input from surrounding cells. Ethanol excitation of DA VTA neurons is associated with a reduction in the action potential afterhyperpolarization (AHP) suggesting that it is due to a decrease in a potassium (K) current which contributes to the AHP. Ethanol excitation is completely blocked by quinidine, but not by the other K channel blockers apamin, tetraethylammonium, barium or cesium. In whole cell voltage clamp experiments, ethanol reduced the sustained outward current evoked by depolarizing voltage steps from aholding potential of-40 mV (to inactivate A-current). These data suggest that ethanol excites DA VTA neurons by reducing a non- or slowly inactivating, quinidine-sensitive, K current of the delayed rectifier type. The specific aims of the present application are two-fold. 1) Electrophysiological and pharmacological characterization of this ethanol- sensitive K current in DA VTA neurons, and determination of the cutoff for ethanol excitation and for reduction of the ethanol-sensitive K current by longer chain length alcohols. 2) Molecular biological studies to try to identify the native ethanol-sensitive K current in terms of cloned K channels of known structure. Candidate channels have been selected according to their electrophysiological and pharmacological similarityto the native channel. RT-PCR on pooled neurons and single cell RT-PCR will be used to determine which candidate channel mRNAs are expressed in DA VTA neurons. Then immunohistochemistrywill be used to see which channel proteins are actually present on the soma and dendrites of DA VTA neurons. Finally, the most likely candidate channels will be expressed in Xenopus oocytes and the electrophysiological properties and cutoff for longer chain alcohols will be determined for these K currents and compared to the properties of the native ethanol-sensitive K current in DA VTA neurons. These data should give important information on the mechanism by which ethanol directly excites DA VTA reward neurons. Taken together, the electrophysiological and molecular biological data should help to identify the ethanol-sensitive native channel on DA VTA reward neurons and therefore point to a gene responsible for its expression. Such a discovery could have major implications for understanding genetic differences in ethanol effects on the mesolimbic reward pathway and how changes in the response of DA VTA neurons during chronic ethanol consumption leads to alcohol craving and addiction.
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2015 — 2019 |
Brodie, Mark S |
P50Activity Code Description: To support any part of the full range of research and development from very basic to clinical; may involve ancillary supportive activities such as protracted patient care necessary to the primary research or R&D effort. The spectrum of activities comprises a multidisciplinary attack on a specific disease entity or biomedical problem area. These grants differ from program project grants in that they are usually developed in response to an announcement of the programmatic needs of an Institute or Division and subsequently receive continuous attention from its staff. Centers may also serve as regional or national resources for special research purposes. |
Epigenetic Mechanisms of Positive Affective State of Alcoholism @ University of Illinois At Chicago
Dopamine is important for the rewarding and reinforcing properties of drugs of abuse, and the ventral tegmental area (VTA) is the source of dopamine to structures in the extended amygdala, including the nucleus accumbens, prefrontal cortex, amygdala and hippocampus. Alcohol-induced alterations of the physiology of neurons of the extended amygdala may underlie the alcohol craving and alcohol seeking associated with alcoholism. Chronic ethanol exposure induces a decrease in sensitivity of dopamine neurons of the VTA to inhibition by gamma aminobutyric acid (GABA) during alcohol withdrawal. Our preliminary data show that this reduction in response to GABA is reversed by treatment with histone deacetylase (HDAC) Inhibitors; this finding indicates that the alcohol-induced change in VTA neurons is maintained by epigenetic mechanisms that can be pharmacologically manipulated. Research Component Project 1 of the CARE plans to examine reduction in GABA-A function in VTA neurons from rats during ethanol withdrawal using electrophysio-^logical and molecular biological methods and to characterize the role of histone acetylation in GABA-A hypofunction during alcohol withdrawal. The goals of this project are: 1) To determine whether GABA hyposensitivity observed during withdrawal is due to increased HDAC activity and reductions in GABA-A receptor subunit expression, 2) To identify whether GABA-A subunit expression, HDAC activity, and histone acetylation are altered during withdrawal from chronic alcohol, and 3) To identify new genes that regulate GABA sensitivity during ethanol withdrawal using RNA sequencing (RNA-seq) and chromatin immunoprecipitation and DNA sequencing (ChlP-seq) in collaboration with the Epigenetic Core. Ultimately, these studies are needed to understand ethanol-induced adaptation of central nervous system neurons involved in addiction, and, with the other components of this Center, will provide a great deal of information on epigenetic mechanisms involved in maintaining alcohol-induced brain changes.
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2020 |
Brodie, Mark S |
P50Activity Code Description: To support any part of the full range of research and development from very basic to clinical; may involve ancillary supportive activities such as protracted patient care necessary to the primary research or R&D effort. The spectrum of activities comprises a multidisciplinary attack on a specific disease entity or biomedical problem area. These grants differ from program project grants in that they are usually developed in response to an announcement of the programmatic needs of an Institute or Division and subsequently receive continuous attention from its staff. Centers may also serve as regional or national resources for special research purposes. |
Epigenetic Mechanisms of Positive Affective State of Aud @ University of Illinois At Chicago
Project Summary As a hallmark of alcohol use disorder (AUD), the withdrawal syndrome includes both negative symptoms like anxiety and motivational symptoms such as craving for alcohol, which promotes relapse and alcohol seeking. Understanding how alcohol withdrawal changes brain physiology is an important step towards developing effective treatments to reduce alcohol abuse. The ventral tegmental area (VTA) is an important brain area that projects to components of the extended amygdala, including the nucleus accumbens, prefrontal cortex, amygdala and hippocampus. Changes in the physiology of VTA neurons induced by withdrawal may underlie the alcohol-seeking during AUD. The sensitivity of neurons of the VTA to inhibition by gamma aminobutyric acid (GABA) is decreased during alcohol withdrawal but normalized by histone deacetylase (HDAC) inhibitors, indicating epigenetic changes induced by withdrawal in the VTA may be amenable to pharmacological manipulation. Whole genome sequencing and molecular studies of this project identified a cluster of genes that encode cholesterol synthesis pathway enzymes that showed decreased expression during alcohol withdrawal, and are functionally relevant to decreased GABA sensitivity in VTA neurons during withdrawal. The proposed project plans to further characterize the role of specific epigenetic modifications in withdrawal-induced regulation of genes responsible for cholesterol synthesis, and the effect of these changes in withdrawal-induced GABA hyposensitivity and drinking behaviors. By using electrophysiological, behavioral, and state of the art molecular biological methods such as chemogenetics and CRISPR technology, we anticipate achieving the following goals: 1) to reveal novel epigenetic marks and changes in gene expression associated with chronic alcohol exposure and withdrawal with whole genome approaches, 2) to examine whether decreased histone acetylation and increased histone methylation reduce expression of cholesterol synthesis enzymes in the VTA during withdrawal in a cell-type specific manner, and probe the role of cholesterol synthesis enzyme genes in withdrawal-related drinking behavior and GABA hyposensitivity, 3) to determine whether targeted epigenetic intervention counteracts withdrawal-induced phenotypes by using CRISPR to prevent decreases in histone acetylation on promoters of key cholesterol synthesis enzyme genes, and 4) to translate to post-mortem human alcoholic VTA the epigenetic dynamics and expression of genes related to GABA hyposensitivity that have been identified in the rat VTA. Ultimately, these studies are needed to understand epigenetic adaptation of VTA neurons involved in the positive affective state during alcohol withdrawal, and, with the other components of this Center, will provide a great deal of information on epigenetic mechanisms involved in withdrawal-induced brain changes, and possible pharmacological approaches toward more effective treatment of AUD.
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