I know this is old, but I wanted to add on to the meditation thing.

I've been a pagan much longer than I've been involved in BDSM, and one of the things I do a lot of is pathworking or guided meditation. Basically, this is a kind of meditation where someone else reads something and you experience it first hand. There are different levels to it, from as close to waking as reading to a more dreamlike experience. I tend to go very deep, compared to others, provided I have a decent lead-in, and when I come out of it, I'm generally cold, stiff, hungry, and have a full bladder (regardless of the lack of drinking during the meditation). I'm very comfortable in space, and find it relatively easy to move from a deeper space to a more "normal" space.

To me, subspace and Domspace are the same thing as this deep meditative space -- it's a heightened awareness of the Reality that is playing out on this deeper, less literal level, where you, for a moment, become what you are playing as a role. The deeper you go, the more real this alternate reality becomes, so there is a danger of abuse if your alternate reality includes things like non-consensuality. For this reason, I tend to go deeper into subspace than I do into Domspace.

I wouldn't say it is endorphins... at least, not the space I go into, since I tend to start going into it right away, at a very mild level through a meditative approach.

However, I realize that this is how I've experienced things, and not necessarily the same thing other people use those names for.