system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What exactly happens when we black out from drinking?
gpt
First of all, it is important to understand that your brain is communicates with itself using neurotransmitters, which relay (transmit) messages around the brain to neurons. 

There are two types of neurotransmitters: excitatory and inhibitory. Excitatory neurotransmitters increase brain activity (through the cascading release of other neurotransmitters, the creation of electrical impulses, etc.). Cocaine acts to increase the activity of dopamine and norepinephrine, two excitatory neurotransmitters. Inhibitory neurotransmitters have the opposite effect. They decrease activity. 

Alcohol potentiates the effect of GABA, which is the brain's primary inhibitory neurotransmitter. This means that every time your brain releases GABA (which it does all the time to regulate itself), alcohol makes the effects of GABA much stronger than normal. When you black out, your brain is prevented from forming lasting memories, as GABA is inhibiting (with heaps of help from all the alcohol, of course) every attempt to do so. That's all a black out is: a void where no lasting memories were able to be formed.