No endorphins, though it probably does release dopamine in your mesolimbic system or something like that, which is why it feels rewarding and can be habit-forming for some, and will also add to the high obviously.
I'm pretty sure wikipedia has a decent article on marijuana's neuropharmacology actually, you should check it out.
But yeah AFAIK it doesn't have anything to do with endorphins, though I can see why you'd think that, people have always told me that the closest feeling drug to opiates is pot.
Edit: according to wiki:
"In addition, it has been shown that cannabinoids, through an unknown mechanism, activate endogenous opioid pathways involving the μ1 opioid receptor, precipitating a dopamine release in the nucleus accumbens. The effects of the drug can be suppressed by the CB1 cannabinoid receptor antagonist rimonabant (SR141716A) as well as opioid receptor antagonists (opioid blockers) naloxone and naloxonazine.[12]"
So I guess it does do something to opioid receptors, but I don't think this is the same thing as endorphins.
Meh I really don' tknow what the hck I'm talking about here, someone more knowledgable will come along.