Since our previous studies showed that mechanical stimulation of a needle inserted into the ulnar tunnel (Guyon’s Canal or HT7 acupuncture Shenmen Point) in the forelimb produces intense and reproducible inhibitory effects on various addictive behaviors caused by cocaine, morphine and ethanol9, 11, 12, 22, a peripheral stimulation was performed as described in our previous experiments11. Mechanical stimulation was performed about 1 min after cocaine injection. Briefly, while an assistant lightly restrained the rat, needles (0.10 mm in diameter, 10 mm in length of needle; Dongbang Medical Co., Korea) were inserted bilaterally 3 mm deep into the ulnar tunnel on the transverse crease of the wrist of the forepaw. By using a newly-developed mechanical instrument that consisted of a custom-made control unit and a mechanical vibrator connected to the needle, the inserted needle was mechanically stimulated for 20 sec in duration at an intensity of 1.3 m/sec2, maintained for 1 min after needle insertion and subsequently withdrawn. Following mechanical stimulation, locomotor activity was monitored for 60 min after cocaine injection. To assess the possibility that the mechanical stimulation of the wrist impaired locomotor behaviors, the radial side of wrist joint was mechanically stimulated in an identical fashion as a control condition.