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Updated: Jun 25, 2026
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A Microbiomechanical System for Studying Varicosity Formation and Recovery in Central Neuron Axons
Published on: April 30, 2018
Large neurohypophysial varicosities amplify action potentials: results from numerical simulations
C Brad Bennett1, Martin Muschol
1Department of Physics, University of South Florida, Tampa, Florida 33620-5700, USA.
Endocrinology
|February 14, 2009
Summary
Large axonal swellings in the neurohypophysis, known as Herring bodies, significantly alter action potential (AP) waveforms. These varicosities amplify AP depolarization, potentially enhancing hormone release from neuroendocrine axons.
Area of Science:
- Neuroscience
- Computational Biology
- Endocrinology
Background:
- Axons in the neurohypophysis exhibit a unique "beads on a string" morphology with secretory swellings.
- Large swellings, termed Herring bodies, are prominent histological features of the neural lobe.
- The physiological function of these large axonal varicosities in neuroendocrine physiology remains largely unknown.
Purpose of the Study:
- To investigate the impact of large in-line axonal varicosities on action potential (AP) waveform and propagation.
- To determine how modulated APs in neurohypophysial axons affect neuroendocrine release.
- To explore the role of varicosity size and ion channel kinetics in AP modulation.
Main Methods:
- Numerical simulations were employed to model AP propagation along neurohypophysial axons.
- Simulation parameters were based on established properties of voltage-gated ion channels in these swellings.
- The study analyzed the effects of single and multiple in-line varicosities on AP waveforms.
Main Results:
- Even a single varicosity can significantly depress AP waveforms upstream.
- AP depolarization is amplified within varicosities, with amplification peaking at Herring body-like diameters.
- Varicosity size is the primary determinant of AP amplification, with ion channel kinetics playing a secondary role.
Conclusions:
- Large axonal varicosities substantially modulate AP waveforms and propagation over long distances.
- The findings suggest that large varicosities are critical sites for enhanced hormone release.
- Different sized varicosities may target distinct neurohypophysial structures for hormone secretion.
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