Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

Short duration presynaptic action potentials shape calcium dynamics and transmitter release at the neuromuscular junction in healthy and diseased states

Ginebaugh, Scott Patrick (2021) Short duration presynaptic action potentials shape calcium dynamics and transmitter release at the neuromuscular junction in healthy and diseased states. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

Download (5MB) | Preview


The action potential (AP) waveform controls the opening of voltage-gated calcium channels (VGCCs) at presynaptic nerve terminals. The calcium ion flux through these VGCCs acts as a second messenger, triggering the release of neurotransmitter. The frog and mouse neuromuscular junctions (NMJs) have long been model synapses for the study of neurotransmission, but the presynaptic AP waveforms from these NMJs have never been recorded because the nerve terminals are too small impale with an electrode for electrophysiological recordings. Neurotransmission from nerve terminals occurs at highly organized structures called active zones (AZs), and the relationships between the AP, VGCCs, and neurotransmission at AZs are poorly understood. Understanding these relationships is important for the study of Lambert-Eaton myasthenic syndrome (LEMS), an autoimmune disorder in which neurotransmitter release from the NMJ is decreased, leading to severe muscle weakness. This reduced neurotransmission is thought to be caused by an antibody-mediated removal of presynaptic VGCCs and disruption of AZ structure. Furthermore, 3,4-diaminopyridine (3,4-DAP; the FDA-approved treatment for LEMS) was thought to indirectly increase calcium flux into the AZs by broadening the presynaptic AP, but this mechanism has come under scrutiny. Here, we use voltage imaging to optically record AP waveforms from frog and mouse motoneuron terminals. We find that the AP waveforms from these terminals are very brief in duration. We hypothesize the brief duration of these APs helps prevent a depletion of docked synaptic vesicles in AZs by limiting calcium flux during APs, and is thus an important mechanism by which healthy NMJs maintain reliable neurotransmission during repeated stimulation. We also show that clinically relevant concentrations of 3,4-DAP increase calcium flux by broadening the AP. Next, we use our recorded AP waveforms to constrain computational models of mammalian AZs, and utilize these models to investigate the effects of LEMS on the AZ. We demonstrate that the disruption of AZ structure plays an essential role in LEMS pathology. Finally, we show that disrupting the calcium-sensing proteins in the AZ could result in LEMS pathology and hypothesize that anti-VGCC antibodies may not be solely responsible for LEMS in many LEMS patients.


Social Networking:
Share |


Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Ginebaugh, Scott Patrickspg30@pitt.eduspg30@pitt.edu0000-0001-8820-606X
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairFaeder, James
Committee MemberFreyberg,
Committee MemberBahar,
Committee MemberLaghaei,
Thesis AdvisorMeriney, Stephen
Date: 31 March 2021
Date Type: Publication
Defense Date: 27 January 2021
Approval Date: 31 March 2021
Submission Date: 3 February 2021
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 199
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Integrative Systems Biology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: neuromuscular junction, voltage imaging, Lambert-Eaton myasthenic syndrome, MCell, calcium dynamics, active zone, action potential, synaptic transmission
Date Deposited: 31 Mar 2021 15:43
Last Modified: 31 Mar 2021 15:43


Monthly Views for the past 3 years

Plum Analytics

Actions (login required)

View Item View Item