Author

Avery Franzen

Author ORCID Identifier

https://orcid.org/0000-0002-6287-4999

Document Type

Dissertation

Date of Award

2025

Degree Name

Doctor of Philosophy (PhD)

Department

Basic Biomedical Science

First Advisor

Brian D Burrell

Abstract

There is a considerable lack in efficacy for current chronic pain treatments. One therapy that has gained attention are cannabinoid-based medications. However, preclinical and clinical trials do not produce anti-nociceptive results consistently and occasionally produce pro-nociceptive results. Understanding this ambiguity between anti-nociceptive and pro-nociceptive effects is vital to cannabinoids’ future utilization. One symptom of chronic pain conditions is allodynia in which pain is perceived following non-painful stimuli. This may be due to non-nociceptive afferents activating nociceptive circuitry in an abnormal manner. Using the medicinal leech, Hirudo verbana, we have begun to elucidate mechanisms by which endocannabinoids strengthen non-nociceptive afferent synapses. Previous work has shown that high-frequency stimulation of a nociceptor causes potentiation not only homosynaptically in the nociceptive synapse, but also heterosynaptically in the non-nociceptive synapses. This heterosynaptic potentiation occurs via endocannabinoid-mediated depression of a GABAergic interneuron that normally inhibits the non-nociceptive synapse. When the inhibitory interneuron is depressed, this disinhibits the non-nociceptive synapse which then potentiates for at least an hour. Paired-pulse facilitation studies indicated that this potentiation was due to postsynaptic mechanisms instead of the presynaptic mechanism that would be expected with just disinhibition. This suggests that there is more than just disinhibition mediating potentiation of the non-nociceptive synapses. Electrophysiological experiments indicated that postsynaptic NMDA receptors and the kinases CamKII, and PKCZ were involved (Chapter 2). To identify and characterize kinases potentially contributing to synaptic plasticity, we searched a Hirudo transcriptome to identify CamKII, PKCZ, PKA, and PKCA and then expressed these kinases and confirmed their ATP-binding ability (Chapter 3). PKCZ and more specifically, its truncated form, PKMZ are exciting targets because PKMZ lacks a regulatory pseudosubstrate. This constitutive function has been thought to contribute to memory formation and may also contribute to chronic pain. However, a barrier to studying PKMZ function for memory or pain is that the current inhibitor of PKMZ lacks specificity and may also inhibit CamKII at higher concentrations. To address this, we performed a high-throughput virtual screen using DOCK6 with molecules from ZINC20. The best binders were then cross-screened against CamKII, PKA, and PKCA to attempt to obtain a specific PKCZ inhibitor.

Subject Categories

Neurosciences

Keywords

Neurosciences

Number of Pages

339

Publisher

University of South Dakota

Available for download on Wednesday, April 30, 2025

Included in

Neurosciences Commons

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