Augmented analgesic effects of L-tryptophan combined with low current transcranial electrostimulation

The analgesic effects of low current transcranial electrostimulation are both naloxone and pCPA-reversible, suggesting that they may be mediated in part by endogenous opioid and serotonergic activity. The present experiments indicate that pretreatment with the serotonin precursor L-tryptophan results in an increased analgesic effect of electrostimulation as measured by the 50 degrees C wet tail flick test in the rat. Rats receiving both L-tryptophan and electrostimulation displayed significantly more analgesia than rats receiving electrostimulation and injection vehicle alone, rats receiving drug and sham stimulation or rats receiving vehicle and sham stimulation.