https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425246/
Resolving the cocaine puzzle? Another puzzle has been that if dopamine does not cause sensory pleasure, why are dopamine-promoting drugs such as cocaine or methamphetamine so pleasant? There are several potential answers, both psychological and neurobiological. A psychological explanation may be that at least some of the euphoria of cocaine or amphetamine drugs comes from a ‘wanting’ component of reward. That is, high incentive salience is just one component used to construct reward experiences (together with high hedonic impact). But on its own, elevated incentive salience induced by dopamine stimulation may to some extent be mistaken for pleasure itself.
Drug enhancement of incentive salience could make other people, events or actions in the world all seem more attractive, and be powerfully enabling of engagement with them, which might well carry an aura of euphoria even if not truly hedonic. Viewed this way, subjective reward experience may be partly synthesized from motivation and cognitive appraisal components, similar to many other emotions (Barrett et al., 2007). This mistaken appraisal explanation may also apply to cases of electrode self-stimulation described below.
A neural explanation for why cocaine is pleasant may be that cocaine and amphetamine also stimulate secondary recruitment of endogenous opioid and related neurobiological hedonic mechanisms, beyond directly raising dopamine release. Those recruited secondary mechanisms may more directly cause ‘liking’ reactions and subjective pleasure. For instance, dopamine-stimulating drugs recruit elevation in nucleus accumbens of endogenous opioid and GABA signals (Colasanti et al., 2012; Soderman and Unterwald, 2009; Tritsch et al., 2012). Elevated endogenous opioid release in a site such as the NAc hedonic hotspot could amplify ‘liking’ as described above, resulting in a more genuinely pleasurable experience. Similarly, GABA signals in the far rostral strip of NAc shell can also enhance true ‘liking’ (Faure et al., 2010), which could occur if drugs of abuse that stimulate dopamine neurons also stimulate some of those neurons to co-release more GABA in NAc (Tritsch et al., 2012).