The DC somatosensory pathway is involved in signaling innocuous information from A-fiber mechanoreceptors that mediate tactile discrimination, well-localized touch, vibration and proprioception14. We and others have provided indirect evidence implicating the DC pathway in the modulation of the midbrain DA system. Stimulation of HT7 acupoint over the ulnar nerve (known as Guyon’s Canal) inhibits cocaine-induced locomotion via activation of A-fiber and also prevents DA release and drug-seeking behaviors by ethanol, cocaine and morphine11–13, 22, 23. Sciatic nerve stimulation at a low threshold current inhibits the activity of most DA neurons in the substantia nigra24. The present study showed that the DC pathway was directly involved in peripheral inhibition of cocaine-induced psychomotor response and suggests a novel functional role of the DC pathway in conveying inhibitory signals from the periphery to the brain reward center. Bilateral stimulation of the forearm radial site did not affect cocaine-induced behaviors, which is consistent with previous studies11, 25. Indeed, it was reported that unilateral stimulation of the radial nerve at low thresholds produces opposite effects on DA activity in anesthetized cats, characterized by DA decrease in the contralateral midbrain and DA increase in the ipsilateral midbrain26. When bilaterally stimulated as in the present study, the radial nerve did not have a significant effect on midbrain DA activity or cocaine-induced psychomotor behaviors.