This study found opposing effects of fentanyl on tonic vs. phasic dopamine that may reveal insight on impaired non-drug reward seeking during opioid exposure
nature.com
Acute fentanyl induces opposing directions of changes in tonic and phasic dopamine release patterns and impairs Pavlovian task performance
Neuropsychopharmacology - Acute fentanyl induces opposing directions of changes in tonic and phasic dopamine release patterns and impairs Pavlovian task performance