U bioengineering professor, Richard Rabbitt, and colleagues showed how the inner ear senses signals such as gravity by examining the involvement of acid (proton concentration) in communication between the neurons and synapses in the brain responsible for feeling gravity and acceleration. Protons are key signaling molecules in synapses responsible for communication between neurons by exchanging chemical or electrical signals.

Led by the Marine Biological Laboratory in Massachusetts at which Rabbitt is an adjunct faculty member, the research team learned the inner ear’s sensory cells continuously communicate the head’s orientation — relative to gravity and low-frequency motion — to the brain.

This type of transmission between sensory cells and target neurons makes it more energy efficient than traditional synapses in which chemical neurotransmitters are bundled in vesicles and released in steps.

The new study was published in the journal “Proceedings of the National Academy of Sciences” on March 25.

“Our findings address how we sense gravity and other low-frequency inertial stimuli, like acceleration of an automobile or roll of an airplane,” explains Rabbitt. “These are very long-lasting signals requiring a synapse that does not fatigue or lose sensitivity over time.”

Rabbitt says the inner ear is the only place where this type of synapse is present. However, because protons play a key role there, they may be important signaling molecules in other synapses elsewhere.

Read study in “Proceedings of the National Academy of Sciences”

See study covered in Medical Xpress

Image courtesy of Wikimedia