David Pearce commented on this post on Facebook:

As an illustration of how much we still don't know: The mu-opioid receptor agonist remifentanil induces acute dysphoria irrespective of its analgesic properties.

Selective activation of the mu opioid receptors by a full mu opioid receptor agonist is the closest recipe we have for pure bliss without desire. But this activation needs to be in the ultimate hedonic hotspots of nucleus accumbens and posterior ventral pallidum. What is the gene expression profile of these cells? Why are they so special?