Tonic gravity changes alter gene expression in the efferent vestibular nucleus

Area of Science:

• Neuroscience
• Vestibular System Physiology
• Space Biology

Background:

• The vestibular system is crucial for balance and spatial orientation.
• Gravity significantly influences vestibular system function.
• Immediate early gene (IEG) proteins are markers of neuronal activity.

Purpose of the Study:

• To investigate the effects of microgravity on efferent vestibular nucleus (EVe) neurons.
• To assess changes in immediate early gene (IEG) protein expression in response to altered gravity.
• To understand the role of EVe neurons in gravity-induced vestibular plasticity.

Main Methods:

• Adult rats were exposed to microgravity aboard the NASA Neurolab Mission (STS-90).
• Control rats were maintained under standard 1g conditions on Earth.
• IEG protein expression in the EVe was quantified at different time points post-flight and post-landing.

Main Results:

• Rats exposed to microgravity showed significantly reduced IEG protein expression in the EVe compared to ground controls.
• Normal levels of IEG protein expression were restored within 1 day of return to Earth.
• IEG protein expression remained normalized at 14 days after landing.

Conclusions:

• Efferent vestibular nucleus (EVe) neurons are sensitive to changes in tonic gravity.
• These neurons play a role in gravity-induced modifications of vestibular hair cell synapses.
• The findings suggest a contribution to the gravity-induced plasticity of the vestibulo-ocular reflex (VOR).