Things that cause a release of dopamine in the mesolimbic pathway may be something pleasurable (sexual stimulation, a bump of cocaine) but also something surprising (drama, whatever is in the package), novel (such as travel), potentially newsworthy (a lottery ticket), or really valuable (oxygen to a deprived organism). In other words, this system alerts us to the anticipation of a meaningful event, not to pleasure per se. Pleasurable stimuli happen to be meaningful, but many other things are also inherently meaningful to an organism that has evolved to survive in ever-changing conditions.
