A COMPARISON OF THE EFFECTS OF HEXAFLUORODIETHYL ETHER AND PENTYLENETETRAZOL ON THE EXCITABILITY OF FROG SKELETAL MUSCLE FIBERS

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Abstract
Hexafluorodiethyl ether (HFE) and pentylenetetrazol (PTZ) differ in their ability to reduce the excitability of the frog's sartorius muscle. HFE increases the threshold current and threshold depolarization necessary for the production of action potentials. At 7.8 mM this drug abolishes the overshoot phase of the action potential and at 23.2 mM it completely blocks the compound action potential response to extracellular stimulation. PTZ is a less potent depressant than is HFE on all the parameters measured. Treating the muscle with 1.5 times the usual concentration of sodium chloride was much more effective in restoring the overshoot potential after HFE depression than after PTZ depression. It is likely that the decrease in overall excitability which results from treatment of the muscle with HFE represents impairment of a sodium-dependent process, whereas depression induced by PTZ, even in very high concentrations, does not. It is suggested on the basis of these results that the very marked central nervous system stimulation which follows parenteral administration of either PTZ or HFE occurs through different mechanisms.