I. Advanced Fluorescent False Neurotransmitters for the Study of Monoamine Transporter Activity and Synaptic Transmission

• Main Author: Karpowicz, Richard
• Language: English
• Published: 2013
• Subjects: Chemistry; Neurosciences
• Online Access: https://doi.org/10.7916/D8ST7P9D

This thesis details two projects at the interface of chemistry and neuroscience. Part I focuses on the development and characterization of fluorescent optical tracers of monoamine neurotransmitters for use in the study of monoamine transporter activity and distribution, as well as synaptic transmission in the brain. The second section details early studies concerning experimental therapeutics recently identified by our group to induce the synthesis and release of Glial Derived Neurotrophic Factor (GDNF) from a model astroglial cell line. Part I consists of Chapters 1-5. Chapter 1 provides a brief introduction to the relationship between chemistry and neuroscience, while explaining the motivation and background behind the development and study of Fluorescent False Neurotransmitters (FFNs). Chapter 2 discusses the characterization of new fluorescent substrates for the Vesicular Monoamine Transporter 2 (VMAT2) for applications in high throughput screening of VMAT activity and inhibition, as well as for imaging aminergic synaptic transmission in brain tissue. Chapter 3 describes the discovery of fluorescent probes FFN201 and AGH093 as dual substrates for the norepinephrine transporter (NET) and VMAT, with potential applications in the imaging of noradrenergic modulation of cortical signaling networks. NG54, a FFN with substrate activity at each of the monoamine transporters was also identified, and represents a new structural class of FFNs. In Chapter 4, APP+, a known fluorescent substrate for the monoamine transporters, is evaluated as a potential tracer of monoamines in the brain. It has been determined that while this molecule may have utility as a marker for monoaminergic neurons, APP+ is not an appropriate FFN due to high background labeling of mitochondria and other intracellular structures. Chapter 5 discusses the discovery of fluorescent substrates of the Organic Cation Transporter 3 (OCT3) and Plasma Membrane Monoamine Transporter (PMAT). Mounting evidence suggests that these transporters play a significant role in clearing extracellular space of monoamines and are likely involved in neurological disease. As such, fluorescent substrates of OCT3 or PMAT would be useful as imaging agents in the brain, as well as for the development of fluorescence-based quantitative inhibition assays. Part II of this thesis (Chapter 6) discusses N-arylethyl isoquinuclidines as releasers of glial cell line-derived neurotrophic factor (GDNF) from a model glial cell line. Initial characterization of GDNF release and its dependence on protein synthesis and MAPK/ERK signaling is described. Preliminary studies indicate that at least two experimental compounds described herein modulate fibroblast growth factor receptor (FGFR) signaling.