Propylene glycol-induced skeletal muscle excitation

The effects of propylene glycol (PG) on frog nerve-muscle preparations were examined to determine whether it has an effect on neuromuscular transmission and, if so, to elucidate the mode of the action. PG (5%, v/v) increased the twitch tension to over twice the control value. PG at concentrations above 0.2% significantly increased the amplitude of the endplate potential. PG (1%) raised the frequency of the miniature endplate potentials and increased their amplitude. These results show that PG both facilitates transmitter release from the nerve terminals and raises the acetylcholine sensitivity of the muscle endplate.