Opioidergic activation in the medial pain system after heat pain.

Opioids modulate the affective component of pain and in vivo data indicate that opioids induce activation changes in the rostral ACC, insula and other brain areas. Hence, opioidergic release is to be expected in these brain regions following experimental pain stimulation. We examined healthy volunteers during heat pain and control subjects during rest using [18F]fluorodiprenorphine-PET. Pain stimulation led to significant reduction of diprenorphine binding in limbic and paralimbic brain areas including the rostral ACC and insula. The finding of altered opioidergic receptor availability in the rostral ACC after experimental nociceptive pain is novel and provides direct evidence for the involvement of this region in endogenous opioidergic inhibition of pain.