There is a long list of hormones and other substances that are released before, during, and following sleep. Many of them are dependent upon ambient light, which is naturally controlled by sunlight (day and night). This changed significantly only a little over a century ago as electric lighting became common in homes & workplaces, raising havoc, for the first time, with human circadian rhythms. So part of it depends on how you take your naps; time of day, light or dark room, blindfolds, etc. (The amount of light necessary to bring about these changes is small enough to penetrate eyelids; even some/most blind people get enough light somehow to effect these changes).

So even if you knew the list of substances, you would then need to determine which one - or ones in combination - out of dozens (hundreds?) produced the effects you mention.

Messing with these substances is risky unless there is a legitimate medical need/reason to supplement them artificially, and even then there are still risks attached - as with anything we take in - there's an equation of benefit vs. risk that needs to be addressed. There are LOTS of natural substances & hormones that we could take artificially that would make us "feel" better/good. Some athletes do it for "performance enhancement", and as with street drugs (and some of the hormones athletes take are now considered street drugs) these substances make the takers feel great at first, and then the hell (and problems) begins....

For example, endorphins (a.k.a. "endogenous morphine") are opioid-like hormones that can make us feel better in a lot of ways, and have many useful functions when released naturally/normally, but too much of them can result in depersonalization disorder, and sudden cessation is believed to play a part in postpartal depression/psychosis.
http://en.wikipedia.org/wiki/Endorphin

Messing with these substances and their delicate balance requires a lot of research, testing, and monitoring, and should only be considered when there is proven medical need and guidance/supervision. The same can be said for many of the supplements and natural substances marketed online and elsewhere. Natural ≠ safe.

Doc

Doc