Doctors have always been looking for new ways to measure a patient’s level of consciousness, and one such method is to analyze the pupil response. Recent research conducted by scientists from ETH Zurich has uncovered the mechanism of this reaction and linked it to orexin neurons.
Orexin, also known as hypocretin, is a neurotransmitter that plays an important role in regulating various processes in the body. Orexin neurons are located in the hypothalamus, a small structure deep within the brain that controls the body’s hormonal responses.
Scientists have found that orexin neurons project through different areas of the brain responsible for arousal and reward. They play an important role in switching between conscious states and sleep states, but their influence on more fleeting states of arousal has not yet been fully understood.
In a study conducted on mice, scientists activated orexin neurons and observed how this affected pupil size. It turned out that activating some of these neurons resulted in pupil dilation. The effect was so obvious that the scientists immediately realized its importance.
Interestingly, some groups of orexin neurons affect not only pupil size, but also the reward system. Moreover, the effects of pupil activation and the reward system are dependent on the dose of stimulation. This indicates a direct link between orexin neurons and the control of pupil dilation.
The scientists also found that noradrenaline neurons, previously thought to be responsible for the pupil response, actually modulate the response of orexin neurons. This links our emotional states and drug responses to the state of our pupils.
An interesting fact is that mice without orexin neurons still had dilated pupils during running, indicating that there is a different nervous system controlling this response.
Orexin neurons play a central role in many body systems, and their damage or loss can lead to a variety of neurological disorders, including sleep disorders and Alzheimer’s disease. The scientists intend to continue research in this area.
The study, published in Nature Neuroscience, opens new horizons in understanding the role of orexin neurons and their influence on pupil response. These results may be useful for the development of new methods of diagnosis and treatment of various neurological disorders.