When you’re in a deep, dream-filled sleep there is something interesting that happens: your muscles become paralyzed.
That’s why you don’t act out what you dream – that’s why you don’t hit your partner in bed when you’re hitting someone in a dream, or why you don’t vividly move your legs when you’re running in a dream.
(Yes, there are occasional exceptions to this mechanism, but these are exceptions that prove the rule, because most of the time we don’t act out what we dream).
Scientists now have found out which chemicals are responsible for paralyzing our muscles during dreams.
University of Toronto researchers Patricia Brooks and John Peever cast a wider net. They focused on two different nerve receptors in the voluntary muscles, one called metabotropic GABAB and one called ionotropic GABAA/glycine. The latter receptor responds to both glycine and a different communication chemical called gamma-aminobutyric acid, or GABA, while the first responds to GABA and not glycine.
The researchers used drugs to “switch off” these receptors in rats and discovered that the only way to prevent sleep paralysis during REM was to shut both types off at the same time. What that means is that glycine alone isn’t enough to paralyze the muscles. You need GABA, too.