Science, Vol 306, Issue 5698, 1029-1032 , 5 November 2004 Nicotine Activation of 4* Receptors: Sufficient for Reward, Tolerance, and Sensitization Andrew R. Tapper,1 Sheri L. McKinney,1 Raad Nashmi,1 Johannes Schwarz,1,2 Purnima Deshpande,1 Cesar Labarca,1 Paul Whiteaker,3 Michael J. Marks,3