[Interaction between opiates and neurotransmitters/neuromodulators in spinal analgesia]

Systematically administered morphine produces its antinociceptive effects through a mechanism involving synergism of the spinal and supraspinal opiate systems. Descending inhibitory monoaminergic pathways, including noradrenergic and serotonergic descending systems, participate in this production of antinociception. Recent studies indicate a synergistic interaction between opiates and adrenergic agonists in the spinal cord. The important consideration arising from the apparent synergy is that significant antinociceptive effects can be achieved with nonspecific doses of either agonist, which alone produces only minimal effects. Though synergy between opiates and adrenergic drugs were principally considered, there remains the possibility of spinal synergistic interactions of opiates and other neurotransmitters/neuromodulators. Since decreasing the effective dosage of analgesics may lessen or eliminate the complications of spinal opiates or other analgesics, these combined effects will be extremely useful for clinical pain management.