Nope. Melatonin is found in the skin. Myelin is found along axons and dendrites alone neurons.
Axons are insulated with a myelin sheath. There are gaps along the myelin sheath called nodes of ranvier. I know this as I major in psychology and am specializing in neuroscience.
No, dreams are nothing more then thoughts when you are sleeping. If you could then there would be people all over talking to each other in their sleep. I tried to get a chicks phone number when I was sleeping once and realized I was in a dream. But it did not work. :-P