2-Minute Neuroscience: Periaqueductal Gray (PAG)

The periaqueductal gray, or PAG, is an area of gray matter that surrounds the cerebral aqueduct in the brainstem. Although it is associated with a number of functions, it is best known for its role in analgesia, or pain reduction. In this video, I discuss the PAG and the pathway by which it is thought to be able to inhibit pain signals from the spinal cord.

TRANSCRIPT:

Welcome to 2 minute neuroscience, where I explain neuroscience topics in 2 minutes or less. In this installment I will discuss the periaqueductal gray, or PAG.

The PAG is an area of gray matter found in a part of the brainstem called the midbrain. The PAG surrounds a structure called the cerebral aqueduct, hence the name “periaqueductal.”

There are a number of functions that have been connected with the PAG, including the regulation of heart rate and blood pressure, management of autonomic processes like bladder control and contraction, production of vocalizations, and production of fearful and defensive reactions. The PAG is best known, however, for its role in analgesia, or pain reduction.

Since the 1960s, the PAG has been known to play a role in analgesia, and stimulation of the PAG has been observed to inhibit pain in both rodents and humans. The mechanisms underlying this PAG-induced analgesia are not completely understood, but the main pathway is thought to involve neurons that project from the PAG to serotonin-producing neurons of the medulla oblongata known as the raphe nuclei. These activated raphe nuclei neurons project down to the dorsal horn of the spinal cord where they inhibit neurons that are responsible for transmitting pain signals. In this way, they inhibit the ability of pain signals to reach the brain.

Through this pathway, the PAG is thought to be able to inhibit pain naturally---a phenomenon that may occur, for example, in situations of extreme stress like that experienced by soldiers in battle. The pathway may also be involved in analgesia that occurs as part of the placebo effect, or in other scenarios where we experience a capacity to control pain through top-down mechanisms. Additionally, the PAG is rich in opioid receptors and believed to play an important role in the analgesia elicited by opioid drugs.

REFERENCES:

Behbehani MM. Functional characteristics of the midbrain periaqueductal gray. Prog Neurobiol. 1995 Aug;46(6):575-605.

[CopperKettle]

Thank you very much, cheers from Russia

[sandraledesma]

Sir thanks a million for your videos, they are perfect for having and overall idea before a lecture of during studying...in just 2 min!!

[Dumbpuppet]

Your channel is my favourite !! Thank you for what you do :-) would be cool to see a behind the scenes of how you create these videos one day, including what inspired you to create these videos too

[rodolfozach]

These instruction presentations are packed with kernels of pearls. Thank you. My question revolves... if it's PAG, G for Gray, why is this zone surrounding the aqueduct depicted as white?

[tvikii]

Thank you for this, your channel is awesome! :)

[sarviljain]

Please can you talk about precuneus also !!

[Rien--]

bruv why am i watching this at 4:13 am

[therationalcollection]

my course doesnt give lectures and just relies on online text books. Im using these vids in replacement of the text book! hopefully i pass :P

[dylancortez]

How the fuck did i get here i just slept