Protons and Potentials: How Neurotransmission Influences and is Influenced by pH Transients

Protons, hydrogen ions, are essential to biological functions, contributing to energy metabolism, protein transport, protein modulation, and ion homeostasis. While usually tightly controlled by systemic and cellular processes, free hydrogen ions can overwhelm endogenous buffering during neurotransmission and can form transient increases or decreases in pH. These transients can modulate neuronal activity by altering neuronal excitability, either by inhibiting or potentiating ion channels or by acting on receptors. Changes in pH and their influence on activity are variable and context dependent, leaving ambiguity on what changes occur and how they may affect neurons. I examined pH transients and how they may affect activity using two preparations: the neuromuscular junctions of the levator auris longus muscle (NMJ) and the central synapses in acute hippocampal brain slices. To characterize transients at the NMJ, I utilized a virally delivered, genetically encoded, pH-sensitive fluorescent probe, pHusion-Ex, to identify a novel activity-dependent pH transient. This transient in the synaptic cleft alkalizes initially and acidifies with more strenuous stimulation. We found that the alkalinizing transient was caused by the activity of plasma membrane Ca2+ ATPases in the NMJ, buffering intracellular release of Ca2+ from the muscle. I also noticed pH changes induced by the neuron did not affect cleft pH, which was expected from prior reports. This led to the hypothesis that there is an additional level of pH regulation within the synaptic cleft, which may be affected in diseases like amyotrophic lateral sclerosis. I then pivoted to investigating how pH affects changes in neurotransmission, beginning by observing spreading depolarization (SD), a wave-like depolarization in the brain that lasts tens of seconds and is thought to be responsible for secondary injury after strokes. I found that extracellular and intracellular pH affect the duration and extent of the SD. I showed that extracellular acidic pH can slow or halt SD, suggesting acidification may be neuroprotective and could be induced clinically to limit SD occurrence following brain injury. This research demonstrates how various factors can alter pH transients, what mechanisms are or could be underlying these changes, and what impacts to neurotransmission may occur due to proton signaling.

Level thesis:degree_level

Doctorate Degree

Year dc:date.issued

2025

Author dc:creator

• Durbin, Ryan Joseph

Advisor dc:contributor.advisor

• Renden, Robert

Committee members dc:contributor.committeemember

• Gould, Thomas
• Mathew, Dennis
• Macleod, Gregory
• Hoy, Jennifer

• Mouse
• Neuromuscular Junction
• pH
• Spreading Depolatization
• Synapse
• Synaptic Transmission

Language dc:language.iso

en_US, English

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/11361

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/11361