Effects of opioid analgesics on local cerebral glucose utilization

The autoradiographic 2-deoxy-D-[1-14C]glucose ([14-C]DG) method was used to map the effects of morphine, oxymorphone and nalbuphine on local cerebral glucose utilization (LCGU), an index of local brain function. The mu agonists (morphine, oxymorphone) decreased LCGU in thalamic nuclei, including some which have been implicated in somatosensory processing. Nalbuphine did not produce these effects, but stimulated LCGU in nuclei of the spinal trigeminal tract. The findings suggest that different supraspinal mechanisms mediate the actions of mu vs. kappa opioids, and that the [14-C]DG procedure is helpful in elucidating the anatomical areas involved.