Catecholamine and serotonin depletion from rat spinal cord: effects on morphine and footshock induced analgesia.

Using a methodology that causes a selective degeneration of spinal cord catecholaminergic or serotoninergic pathways but not those of the brain, it has been possible to study more precisely the role played by the spinal cord monoaminergic systems that underly the mechanism through which morphine and endogenous opioids modulate nociceptive inputs. Both noradrenaline (NA) and serotonin (5-HT) appear to be involved: first, the noradrenergic and only subsequently, with higher doses of the opiate, the serotoninergic pathways.