I wanted to resurrect some discussion on AH-7921, specially if anyone knows if it affects other non-opioid receptors. My post contains a bit of a trip report (sorry!), but I felt it was needed to understand the context of my question.
I've had a chance to try AH-7921 out, dosing multiple times over the past few days... it is an odd, fascinating, and enjoyable little compound. It definitely has an opiate feel to it, especially at higher doses, but I would bet $ that it is very promiscuous with respect to receptor types affected. At lower doses (30-60mg) it felt sedating with a heavy body load. It also exhibited some dissociative effects (almost like a threshold ketamine dose), left me very introverted socially, and bordered on being dysphoric.
At slightly higher doses (75-100mg) it had a real GABAnergic character to it with neutral/elevated mood, pro-social & anxiolytic. Mixing it with 1-2 EtOH drinks exaggerated these qualities and i had to fight the urge to slide into sleep, with maybe some memory loss (!!).
Pushing the dose even higher (100 + 50mg 2 hr later) brought on a full out opiate-type high. Euphoria, itching, pupil constriction, the "nods" with beautiful vivid dream imagery (compatible only to one past experience with smoked opium), and energetic. I'd compare this dose to 40-60mg oxycodone + 1mg of xanax (as it still had the GABAnergc type effects).
It wasn't reinforcing per se (fiending/craving/etc) but I found myself taking way more than I meant to. E.g., would plan on taking 75 mg + 5 mg at T=1 hr. I'd take the 5 mg, forget that I had taken it, take another 5 mg, forget that I had taken it, etc etc. This sort of behaviour happens to me on benzos, but never on opiates.