Motion sickness is an unpleasant sensation that afflicts many individuals, causing nausea, dizziness, and other discomforting symptoms. While we may be familiar with the experience, the underlying mechanisms behind motion sickness are still not fully understood. In a groundbreaking study, researchers from the Autonomous University of Barcelona turned their attention to mice, subjecting them to a rotating spinner to pinpoint the brain cells responsible for motion sickness. The results of this study have provided intriguing insights into the neural pathways involved in this prevalent ailment.
To embark on their investigation, neuroscientist Pablo Machuca-Márquez and his colleagues focused on the vestibular nuclei, a collection of nerve fibers in the brainstem that transmit signals from the ear to the brain. These signals play a crucial role in our brain’s ability to orientate ourselves during movement. It is hypothesized that a mismatch between sensory inputs from the eyes, inner ear, and limbs gives rise to motion sickness. By honing in on the specific neurons within the vestibular nuclei responsible for this response, the researchers aimed to pave the way for the development of more targeted and effective medications.
To identify the neurons associated with motion sickness, the researchers experimented with inhibiting different subsets of neurons in the vestibular nuclei. They observed the behavior of the mice after the neural inhibition and the subsequent exposure to the spinning apparatus. Surprisingly, they found that inactivating a certain group of vestibular neurons that express the protein VGLUT2 prevented the mice from experiencing motion sickness induced by the spinning. Conversely, by stimulating these same neurons, the researchers were able to trigger motion sickness-like behaviors in the absence of any actual spinning.
Among the VGLUT2-expressing neurons, the researchers discovered that cells sprouting a receptor called CCK-A were primarily responsible for eliciting motion sickness behaviors. Further investigation led them to map the circuitry of these neurons, revealing their dense projections into a brain region called the parabrachial nuclei. This area is known for regulating appetite suppression, body temperature, and lethargy. Stimulating these projections induced certain symptoms of motion sickness in the mice, such as decreased body temperature and aversion to sugary foods.
By blocking the CCK-A receptor with a drug compound before subjecting the mice to the spinning apparatus, the researchers observed a significant reduction in the activity of brain cells in the parabrachial nuclei. This blockade also alleviated some of the motion sickness behaviors in the mice. These findings hold considerable promise for the development of new medications that can more specifically target the neural pathways associated with motion sickness, potentially offering relief without the unwanted side effects often encountered with current treatments.
While this study was conducted on mice, there is a strong possibility that the uncovered pathways function similarly in humans. If this holds true, the newfound understanding of the neural mechanisms behind motion sickness could significantly aid in the development of more effective treatments. Notably, NASA’s ongoing research on a fast-acting nasal spray to combat motion sickness aligns with this direction of exploration. The potential for clearer and more targeted interventions brings hope to individuals who suffer from motion-induced discomfort, paving the way for a future with improved solutions.
The study on motion sickness in mice has shed light on the intricate workings of the brain that contribute to this pervasive ailment. By identifying the role of specific neurons, such as those expressing the CCK-A receptor, and mapping their connections within the brain, researchers have unraveled key components of the neural circuitry underlying motion sickness. These findings offer exciting prospects for the development of novel medications with greater efficacy and fewer side effects. As further studies unfold, we may be edging closer to a future where motion sickness will become a less formidable obstacle for individuals navigating winding roads and adventurous journeys.