Ephaptic coupling
In 1941 Angélique Arvanitaki[5] explored the same topic and proposed the usage of the term "ephapse" (from the Greek ephapsis and meaning "to touch") to describe this phenomenon and distinguish it from synaptic transmission.
Over time the term ephaptic coupling has come to be used not only in cases of electric interaction between adjacent elements, but also more generally to describe the effects induced by any field changes along the cell membrane.
[12] It was also shown that such unidirectional synchronization or copy/paste transfer of neural dynamics from master to slave neurons, could be exhibited in different ways.
A study in July 2023 found that mathematical models of ephaptic coupling predicted in vivo data of neural activity.
Hence it is a hypothesis that neurobiology and evolution of brain coped with ways of preventing such synchronous behavior on large scale, using it rather in other special cases.
The proximity of sodium channels to gap junction plaques has been shown to relate to their effectiveness in driving ephaptic coupling action potential transmission.
[18] Experimental work suggests that sodium channel-rich nanodomains located at sites of close contact between cardiac myocytes may constitute functional units of ephaptic coupling and selective disruption of these nanodomains resulted in arrhythmogenic conduction slowing, suggesting an important role for ephaptic coupling in the heart.
One study suggested that cortical cells represent an ideal place to observe ephaptic coupling due to the tight packing of axons, which allows for interactions between their electrical fields.
[22] Later, a model was created to predict this phenomenon and showed scenarios with greater extracellular spacing that effectively blocked epileptic synchronization in the brain.
A number of studies have shown how inhibition among neurons in the olfactory system works to fine-tune integration of signals in response to odor.
The inhibition due to ephaptic coupling would help account for the integration of signals that gives rise to more nuanced perception of smells.
[28] Due to the very small electrical fields produced by neurons, mathematical models are often used in order to test a number of manipulations.
[29] It calculates electric current using capacitance and resistance as variables and has been the main basis for many predictions about ephaptic coupling in neurons.
The level of transmission varied, from subthreshold changes to initiation of an action potential in a neighboring cell, but in all cases, it was apparent that there are implications of ephaptic coupling that are of physiological importance.
These findings support a model in which ephaptic coupling works alongside canonical synapses to propagate signals across neuronal networks.
[33] One of the few known cases of a functional system in which ephaptic coupling is responsible for an observable physiological event is in the Purkinje cells of the rat cerebellum.
[24] While many supporters of the ephaptic coupling theory have been trying to prove its existence through experiments that block both chemical and electrical synapses, still some opponents in the field express caution.
Assuming the reproducibility of this experiment skeptics of ephaptic coupling should be satisfied it is a real phenomenon and investigations will focus now on its mechanisms and role rather than its existence.
