Action of Alcohol in the Brain
Why does alcohol relax?
Silvia Helena Cardoso, PhD e RenatoM. E. Sabbatini, PhD
André Luis Malavazzi (artee animação)
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Alcohol seems to act upon existing channelsin the neuron membrane, where these cells exchange ions with the environment.Through them, positive or negative ions enter or leave the neuron, thusenhancing or diminishing their electric activity.
This process, on its turn, affects allbrain functions. Normally, ionic channels are opened or closed by the actionof neurotransmitters or by variations in the electric potential gradientbetween the interior and exterior of the neurons.
When ethanol links to the GABA receptor( the channel shown in violet-blue in the image in the middle) it promotesa facilitating action of GABA inhibition. The result is a furtherinhibitory effect upon the brain, leading to relaxation and sedation ofthe organism. Several parts of the brain are affected by the sedative effectof alcohol such as those responsible for movement, memory, reasoning, respirationand so on, because there are GABA receptors in many parts of the brain. The sustained usage of alcohol can lead to dependency. Then, if the personstops drinking, he will experience emotional discomfort, anxiety, trembling,insomnia.
Why does alcohol relax?
Although the relaxing effect of alcoholis well known, until recently nobody could quite explain it exactly.
The reason - that has just been publishedin the journal Nature - was discovered by a team of researchers led by Toru Kobayashi, from Niigata University, in Japan and Joanne Lewohl, fromTexas University, in the USA.
The researchers demonstrated that alcoholopens a specific type of ionic channel, called GIRK. When open, this channelallows that brain cells eliminate potassium, thus reducing their activity.The result is a slow-down in brain function, perceived as a relaxing sensationby the drinker.
The direct action of alcohol has onlybeen confirmed in relation to this specific phenomenon. Other effects ofthe drug, such as the diminishing motor control, are indirectly causedand required the agency of neurotransmitters or the changing in voltageof neuron's membranes.
