The drugs well lets start with brain chemicals dopamine and noradrenaline. This work on the neurotransmitters noradrenaline known as Epinephrine and is a hormone. It works on the nervous system in the fight flight responses.
Dopamine is a neurohormone and has many functions in the brain and it seems one of them may be reward/ punishment predictor. When we get a child or animal to perform a task and relate that learning to a reward.
Man made drugs will have their normal effects of heightening or decreasing these hormone levels of the bodies own drugs. Possibly the most constant companion man-made drug to gambling is alcohol and it can be your worst enemy. Alcohol changes your risk perception irrespective of your normal attitude toward risk. We all know of friends who become emboldened by drinking and those who become depressed again changing the risk perception. Therefore, alcohol needs to be moderated when gambling. So gambling is a risky business and drugs increase the risk whether produced by the body or manufactured.
Now can the risk be reduced whilst still producing levels of euphoria and depression without financial risk? The answer of course is yes. Just learning a game and winning gives you a high or a low irrespective of any gambling wagers on the game.
There are many sites out there offering free-play options, from online casino sites to social network sites such as face-book. Of course the aim of all this is to draw the user into to the hard gambling side of the business where they make their profits. So it comes down to you. Can you exercise control? Can you accept gratification just from the act of winning, and accept losing with a shrug of the shoulders and knowing you lost nothing. Perhaps in that scenario receiving a low followed by a slight high we call relief.