Our overall objective is to develop new bioanalytical methods for exploring brain chemistry dynamics in vivo. Neurons and glia in the brain communicate by releasing neurotransmitters that interact with receptors on neighboring cells. Monitoring the concentration dynamics of neurochemicals and metabolites in vivo is a vital tool in the effort to understand brain function, diseases, and treatments. A versatile and effective approach for in vivo monitoring of chemical messages is to couple sampling methods, such as microdialysis, to analytical measurements. Although this approach has proven invaluable, its utility is limited by poor temporal resolution, poor spatial resolution, poor results for neuropeptide monitoring, and application to only acute measurements. In this project, we will develop technology and methods to solve these problems. Temporal resolution is important because concentrations of transmitters can change rapidly during behavior and experimental maneuvers. Temporal resolution is often limited by dispersion of concentration pulses as they are transported to the analytical system. We will develop a microfluidic sampling system whereby the aqueous sample stream is segmented into droplets within a stream of oil and the droplets subsequently analyzed by rapid chip-based electrophoresis assays. Sample stream segmentation will prevent dispersion during mass transport and allow temporal resolution of 10 s or better for many neurotransmitters. This system will be coupled to miniaturized sampling probes to improve spatial resolution and allow access to small brain regions. Neuropeptides regulate many brain functions;however, monitoring them in vivo is limited by the sensitivity of current methods so that samples must be collected for ~30 min resulting in poor temporal resolution. We will develop high sensitivity neuropeptide assays based on capillary liquid chromatography and microfluidic immunoassays. The assays will have detection limits of 1 pM for 1 ?L samples allowing an unprecedented 10-fold improvement in temporal resolution for neuropeptide monitoring. In vivo chemical measurements are nearly always performed acutely;however, it would be extremely useful to be able to monitor neurochemistry over a period of weeks to monitor progressive changes associated with diseases, like addiction, or normal function, like learning. Long term monitoring is typically prevented by reactive gliosis, a tissue reaction that results in encapsulation of the probe and prevents sampling from active neural tissue. We will explore the use of pharmacological interventions with compounds known to suppress reactive gliosis and support neuroregeneration to prolong in vivo monitoring. Finally, we will perform fundamental neuroscience studies as a means of testing the methods and demonstrating their utility to the broader neuroscience community. These applications include determining: 1) the role of leptin receptors in regulating dopamine and feeding behavior;2) the effect of psychostimulants on opioid peptides, and 3) neurochemical differences underlying distinct behavioral phenotypes that are a model for vulnerability to drug addiction. Mental illnesses and neurological diseases comprise some of the most devastating and expensive to treat disorders in modern society. Determining the neurochemical imbalances underlying such disorders is a key step in developing appropriate therapies;however, in most cases the neurochemistry is not well understood. In this project, we are developing novel instrumentation and techniques that enable neurochemicals to be monitored in the living brain. These new methods will enable important questions to be addressed relating to underlying causes of diseases involving the brain as diverse as addiction, Huntington's disease, and obesity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37EB003320-14
Application #
8013803
Study Section
Enabling Bioanalytical and Biophysical Technologies Study Section (EBT)
Program Officer
Korte, Brenda
Project Start
1999-05-05
Project End
2013-01-31
Budget Start
2011-02-01
Budget End
2012-01-31
Support Year
14
Fiscal Year
2011
Total Cost
$392,392
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Carpenter, Colleen; Zestos, Alexander G; Altshuler, Rachel et al. (2017) Direct and Systemic Administration of a CNS-Permeant Tamoxifen Analog Reduces Amphetamine-Induced Dopamine Release and Reinforcing Effects. Neuropsychopharmacology 42:1940-1949
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Lee, Woong Hee; Ngernsutivorakul, Thitaphat; Mabrouk, Omar S et al. (2016) Microfabrication and in Vivo Performance of a Microdialysis Probe with Embedded Membrane. Anal Chem 88:1230-7
Hamid, Arif A; Pettibone, Jeffrey R; Mabrouk, Omar S et al. (2016) Mesolimbic dopamine signals the value of work. Nat Neurosci 19:117-26
Cui, Qiaoling; Pitt, Jason E; Pamukcu, Arin et al. (2016) Blunted mGluR Activation Disinhibits Striatopallidal Transmission in Parkinsonian Mice. Cell Rep 17:2431-2444

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