Sensing gravity with acid: Scientists discover a role for protons in neurotransmission

March 25, 2014
toadfish
The toadfish (Opsanus tau) is a model organism used by the Highstein lab to study hearing, balance, and synaptic transmission. Credit: Wikimedia

While probing how organisms sense gravity and acceleration, scientists at the Marine Biological Laboratory (MBL) and the University of Utah uncovered evidence that acid (proton concentration) plays a key role in communication between neurons. The surprising discovery is reported this week in Proceedings of the National Academy of Sciences.

The team, led by the late MBL senior scientist Stephen M. Highstein, discovered that sensory cells in the continuously transmit information on orientation of the head relative to gravity and low-frequency motion to the brain using protons as the key synaptic signaling molecule. (The synapse is the structure that allows one neuron to communicate with another by passing a chemical or electrical signal between them.)

"This addresses how we sense gravity and other low-frequency inertial stimuli, like acceleration of an automobile or roll of an airplane," says co-author Richard Rabbitt, a professor at University of Utah and adjunct faculty member in the MBL's Program in Sensory Physiology and Behavior. "These are very long-lasting signals requiring a synapse that does not fatigue or lose sensitivity over time. Use of protons to acidify the space between cells and transmit information from one cell to another could explain how the inner ear is able to sense tonic signals, such as gravity, in a robust and energy efficient way."

The team found that this novel mode of neurotransmission between the (type 1 vestibular hair cells) and their target afferent neurons (calyx nerve terminals), which send signals to the brain, is continuous or nonquantal. This nonquantal transmission is unusual and, for low-frequency stimuli like gravity, is more energy efficient than traditional synapses in which chemical neurotransmitters are packaged in vesicles and released quantally.

The calyx nerve terminal has a ball-in-socket shape that envelopes the sensory hair cell and helps to capture protons exiting the cell. "The inner-ear vestibular system is the only place where this particular type of synapse is present," Rabbitt says. "But the fact that protons are playing a key role here suggests they are likely to act as important signaling molecules in other synapses as well."

Previously, Erik Jorgensen of University of Utah (who recently received a Lillie Research Innovation Award from the MBL and the University of Chicago) and colleagues discovered that protons act as signaling molecules between muscle cells in the worm C. elegans and play an important role in muscle contraction. The present paper is the first to demonstrate that protons also act directly as a nonquantal chemical neurotransmitter in concert with classical neurotransmission mechanisms. The discovery suggests that similar intercellular proton signaling mechanisms might be at play in the central nervous system.

Stephen Highstein, who died in January 2014, was associate director of the MBL's Program in Sensory Physiology and Behavior. Mary Anne Mann, a research associate in the program, also participated in this research, as did Gay Holstein of Mt. Sinai School of Medicine.

Explore further: Researchers create the inner ear from stem cells, opening potential for new treatments

More information: Highstein SM, Holstein GR, Mann MA, and Rabbitt RD (2014) Evidence that protons act as neurotransmitters at vestibular hair cell-calyx afferent synapses. PNAS doi/10.1073/pnas.1319561111

Related Stories

Researchers create the inner ear from stem cells, opening potential for new treatments

July 10, 2013
Indiana University scientists have transformed mouse embryonic stem cells into key structures of the inner ear. The discovery provides new insights into the sensory organ's developmental process and sets the stage for laboratory ...

Animal cells can communicate by reaching out and touching, team discovers

January 2, 2014
In a finding that directly contradicts the standard biological model of animal cell communication, UCSF scientists have discovered that typical cells in animals have the ability to transmit and receive biological signals ...

Building the best brain: Researchers show how brain cell connections get cemented early in life

September 20, 2013
When we're born, our brains aren't very organized. Every brain cell talks to lots of other nearby cells, sending and receiving signals across connections called synapses.

Recommended for you

The neural codes for body movements

July 21, 2017
A small patch of neurons in the brain can encode the movements of many body parts, according to researchers in the laboratory of Caltech's Richard Andersen, James G. Boswell Professor of Neuroscience, Tianqiao and Chrissy ...

Faulty support cells disrupt communication in brains of people with schizophrenia

July 20, 2017
New research has identified the culprit behind the wiring problems in the brains of people with schizophrenia. When researchers transplanted human brain cells generated from individuals diagnosed with childhood-onset schizophrenia ...

Scientists reveal how patterns of brain activity direct specific body movements

July 20, 2017
New research by Columbia scientists offers fresh insight into how the brain tells the body to move, from simple behaviors like walking, to trained movements that may take years to master. The discovery in mice advances knowledge ...

Scientists discover combined sensory map for heat, humidity in fly brain

July 20, 2017
Northwestern University neuroscientists now can visualize how fruit flies sense and process humidity and temperature together through a "sensory map" within their brains, according to new research.

Team traces masculinization in mice to estrogen receptor in inhibitory neurons

July 20, 2017
Researchers at Cold Spring Harbor Laboratory (CSHL) have opened a black box in the brain whose contents explain one of the remarkable yet mysterious facts of life.

Speech language therapy delivered through the Internet leads to similar improvements as in-person treatment

July 20, 2017
Telerehabilitation helps healthcare professionals reach more patients in need, but some worry it doesn't offer the same quality of care as in-person treatment. This isn't the case, according to recent research by Baycrest.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.