Sensitivity of excitable and inexcitable membranes to alpha-dihydrograyanotoxin II

A variety of excitable and inexcitable preparations have been examined for their sensitivity to the depolarizing action of alpha-dihydrograyanotoxin II. alpha-Dihydrograyanotoxin II was effective in producing membrane depolarization in giant axons from the crayfish (Procambarus clarki) and sartorius muscle fibers from the frog (Rana pipiens) and the salamander (Taricha torosa). The toxin-induced depolarization was reversed by lowering the external sodium concentration. High concentrations of tetrodotoxin and saxitoxin were also effective in reversing the depolarization in the various grayanotoxin-sensitive preparations studied except in the salamander sartorius muscle, in which sodium-dependent action potentials were highly resistant to tetrodotoxin and saxitoxin. In contrast, alpha-dihydrograyanotoxin II was ineffective in changing the resting membrane potential in the muscle fibers of the crayfish (Procambarus clarki and Orconectes virilis) and in the salivary gland giant cells from Drosophila virilis. Of the preparations that were examined, only the membranes that produce a sodium-dependent action potential are sensitive to the depolarizing action of alpha-dihydrograyanotoxin II.