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.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Method to Extend Research in Time (MERIT) Award (R37)
Project #
Application #
Study Section
Enabling Bioanalytical and Biophysical Technologies Study Section (EBT)
Program Officer
Korte, Brenda
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Michigan Ann Arbor
Schools of Arts and Sciences
Ann Arbor
United States
Zip Code
Mabrouk, Omar S; Semaan, Daniel Z; Mikelman, Sarah et al. (2014) Amphetamine stimulates movement through thalamocortical glutamate release. J Neurochem 128:152-61
Bosse, Kelly E; Jutkiewicz, Emily M; Schultz-Kuszak, Kristin N et al. (2014) Synergistic activity between the delta-opioid agonist SNC80 and amphetamine occurs via a glutamatergic NMDA-receptor dependent mechanism. Neuropharmacology 77:19-27
Zhou, Ying; Mabrouk, Omar S; Kennedy, Robert T (2013) Rapid preconcentration for liquid chromatography-mass spectrometry assay of trace level neuropeptides. J Am Soc Mass Spectrom 24:1700-9
Kennedy, Robert T (2013) Emerging trends in in vivo neurochemical monitoring by microdialysis. Curr Opin Chem Biol 17:860-7
Slaney, Thomas R; Mabrouk, Omar S; Porter-Stransky, Kirsten A et al. (2013) Chemical gradients within brain extracellular space measured using low flow push-pull perfusion sampling in vivo. ACS Chem Neurosci 4:321-9
Hershey, Neil D; Kennedy, Robert T (2013) In vivo calibration of microdialysis using infusion of stable-isotope labeled neurotransmitters. ACS Chem Neurosci 4:729-36
Lee, Woong Hee; Slaney, Thomas R; Hower, Robert W et al. (2013) Microfabricated sampling probes for in vivo monitoring of neurotransmitters. Anal Chem 85:3828-31
Hesdorffer, Charles S; Malchinkhuu, Enkhzol; Biragyn, Arya et al. (2012) Distinctive immunoregulatory effects of adenosine on T cells of older humans. FASEB J 26:1301-10
Song, Peng; Mabrouk, Omar S; Hershey, Neil D et al. (2012) In vivo neurochemical monitoring using benzoyl chloride derivatization and liquid chromatography-mass spectrometry. Anal Chem 84:412-9
Slaney, Thomas R; Nie, Jing; Hershey, Neil D et al. (2011) Push-pull perfusion sampling with segmented flow for high temporal and spatial resolution in vivo chemical monitoring. Anal Chem 83:5207-13

Showing the most recent 10 out of 23 publications