Influence of vitamin B1 (thiamine) antagonists pyrithiamine and oxythiamine on synaptic transmission in mice diaphragmatic muscle was investigated. In isolated phrenico-hemidiaphragmatic preparations obtained from animals intraperitoneally injected with 100 mg/kg pyrithiamine 1.5 hours earlier, the amplitudes of miniature end-plate potentials (mEPPs) and end-plate potentials (EPPs), as well as quantal content of EPP, were significantly smaller than in the control. In preparations obtained 3 and 24 hrs but not 72 hrs after subcutaneous injection of 400 mg/kg oxythiamine, the amplitude of EPPs and their quantal content were significantly smaller than in the control. Pyrithiamine but not oxythiamine reproduces neuromuscular transmission disturbances, characteristic for severe alimentary vitamin B1 deficiency.
