Propylene glycol (PG) is widely used as a solvent for injections. However, there are a few reports describing severe toxic effects of PG on human nervous tissues. To elucidate its mechanism, the present study has been conducted to determine whether PG enhances the release of catecholamine in PC12 cells. When the incubation time was longer than 3 min, PG significantly facilitated the dopamine release. PG (0.2-20 %v/v) concentration-dependently increased the dopamine release and the effects of PG at the concentrations above 1% were significant. High K+ (50 mM) and carbamylcholine (50 microM) increased the dopamine release. High K+ and electrical stimulation augmented the action of PG. Tetrodotoxin (1 microM) had no effect on the PG action. In conclusion, PG enhances the dopamine release. It is suggested that the facilitation of the transmitter release from the motor nerve terminals may be related to the PG-evoked skin twitch.