A natural reaction to being grabbed or bitten, even play- fully, is to swat at the cat. Don't do this! Physical punishment may cause your cat either to fear you or to engage in even rougher play. If your cat becomes afraid of you, you may face a bigger problem--that of defensive aggression. If the attack can be anticipated, a blast of air from a compressed air can (obtained from a photography store), a squirt from a water gun, or the noise of an audible alarm or a shaker can (an empty soda can with pennies in it) may discourage the behavior if produced at the moment of the attack. Timing is everything. If "fired" a second or two after the incident, the deterrent will not be connected with the attack in the cat's mind and no training will take place, although the cat may be frightened and confused. 

 Perhaps the best deterrent is the one that is always at hand--one's voice. A loud and shrill "Eek", followed by a sharp "No!" can be very effective with some cats. The next step is to shun the cat for the next ten minutes. This means paying
absolutely no attention to the cat. Don't lecture or scold the cat and don't pick it up to put it in a separate room. Any
attention at this point can be reinforcing, so totally ignore the cat. This is precisely the way a kitten learns to inhibit his biting when playing with another kitten. If one becomes a little too rough, the victim will squeal and run away. The aggressor will watch his playmate run away and wonder what happened. Eventually he learns that if he wants to extend the play session  (which he always wants to do), then he will have to be more gentle. 

This training method works well--if you are patient and consistent.