# Identifying the mechanisms causal to nonequivalent release sites at zebrafish neuromuscular junctions

> **NIH NIH R01** · OREGON HEALTH & SCIENCE UNIVERSITY · 2020 · $336,875

## Abstract

The advantages provided by the zebrafish neuromuscular synapse have led to discoveries that have
greatly advanced our basic understanding of neurotransmission and neuromuscular diseases.
Driving all our studies has been our development of paired motoneuron muscle patch clamp
recordings, which has only been possible in zebrafish. We recently used this methodology to explore
frequency-dependent depression, one of the most prevalent forms of synaptic plasticity, and
obtained evidence for heterogeneity among release sites. The existence of functionally distinct
classes of release sites remains an unexplored territory among vertebrates, calling for development
of probes adequate to detect their function. Also unique to zebrafish neuromuscular junction is a
small number of release sites that are well separated from one another. To probe each of these
release sites independently we created a transgenic line wherein the calcium indicator GCaMP6f is
fused to postsynaptic rapsyn. Due to the high calcium permeability of the nicotinic receptor, we have
been able to optically track release of single quanta from individual motoneuron release sites. With
this powerful detector, we now outline a series of experiments that will test for release site
heterogeneity and its role in synaptic depression. We also utilize optical quantal analysis to further
address an outstanding question asking whether the synchronous, asynchronous and spontaneous
modes of synaptic transmission work through the same or different release sites. Finally, to identify
the structural counterparts of functional heterogeneity, we are collaborating with Christian Stigloher,
an expert in high-resolution tomographic analysis of zebrafish neuromuscular synapses. Individual
fast and slow synapses will be identified on the basis of optical quantal analysis and subjected to
tomographic reconstruction to test for differences in cytomatrix components of the active release
site. Only through the many unique features offered by this vertebrate cholinergic synapse is it
possible to perform the proposed experiments to decipher synaptic depression and associated use
dependent fatigue, common to almost all myasthenias.

## Key facts

- **NIH application ID:** 9963396
- **Project number:** 5R01NS105664-03
- **Recipient organization:** OREGON HEALTH & SCIENCE UNIVERSITY
- **Principal Investigator:** PAUL BREHM
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $336,875
- **Award type:** 5
- **Project period:** 2018-09-30 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9963396

## Citation

> US National Institutes of Health, RePORTER application 9963396, Identifying the mechanisms causal to nonequivalent release sites at zebrafish neuromuscular junctions (5R01NS105664-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9963396. Licensed CC0.

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