during sleep, you have incredible peaks in acetylcholine and drops in acetylcholine. You have incredible peaks in dopamine and drops in dopamine. You have incredible peaks in serotonin and drops in serotonin. Most often, you are not going to see much if any release of epinephrine, adrenaline, and that's because epinephrine, also called adrenaline, tends to wake us up and put us into action mode behaviors and that's simply not happening during sleep.