Complex sentence: Caffeine's mechanism of action is somewhat different from that of other addictive stimulants, cocaine and the substituted amphetamines; caffeine blocks adenosine receptors A and A2A.
Split into simpler sentences: Caffeine's mechanism of action is somewhat different from that of other addictive stimulants, cocaine and the substituted amphetamines. Caffeine blocks adenosine receptors A and A2A.