Antagonism of non-depolarization muscle relaxants and aminoglycoside antibiotics to the block of neuromuscular junction of the rat diaphragm caused by soman

Subparalytic concentrations of dTC (0.05-0.25 microM), gallamine triethiodide (5.6-44.8 microM), pacuronium(0.21-0.65 microM), streptomycin( 100-500 microM), neomycin(80-320 microM) and kanamycin ( 1 microM) partially or completely antagonized tetanus block and other variations caused by 11 microM soman in isolated rat’s phrenic nerve-diaphragm preparations. In vivo, 10 mg/kg gallamine or 300 mg/kg streptomycin im protected or restored the indirect elicited (50 Hz, 0.3 s)rat’s diaphragm action potentials which could be abolished by 2 microg soman given onto the endplat regions of the ipsilateral diaphragm. No-depolarization agents and aminoglycoside antibiotics manifested different antagonistic feature. The combination of 22.4 microM gallamine and 200 microM streptomycin (in vitro), 5 mg/kg gallamine and 100 mg/kg streptomycin( in vivo) antagonized the affects of soman completely. In the isolated and chronically denervated rat’s diaphragm muscle, 0.2 microM Dtc or 22.4 microM gallamine inhibited the contraction induced by 56 microM Ach, but 500 microM streptomycin did not. It is proposed that the effects of dTC and gallamine against soman are mainly due to their postsynaptic receptor action, but that of streptomycin may be substantially owing to its presynaptic action.