Abstract
The effect of maitotoxin (MTX), the most potent marine toxin as yet known, was studied using the skeletal muscle of the larval meal worm,Tenebrio molitor. In normal saline,Tenebrio muscles responded with the spike to direct stimulation. In the saline containing tetraethylammonium (TEA) the all-or-none action potential which had characteristic plateau was elicited by membrane depolarization. When MTX (5×10−9 to 10−8 g/ml) in the TEA saline was added, the plateau of action potential was prolonged more than in the saline containing TEA alone. Furthermore, MTX lowered the threshold, so that action potentials were readily evoked in the saline containing MTX. In either case, effects, of MTX were antagonized by Co2+. These results suggest that MTX activates the voltage-dependent Ca2+ channels in the insect muscle.
Similar content being viewed by others
References
Deitmer JW (1977) Effects of cobalt and manganese of the calcium-action potentials in larval insect muscle fibers (Ephestia kulniella). Comp Biochem Physiol 58A:1–4
Hagiwara S, Byerly L (1981) Calcium channel. Ann Rev Neurosci 4:69–125
Ohizumi Y, Kajiwara A, Yasumoto T (1983) Excitatory effect of the most potent marine toxin, maitotoxin, on the guineapig vas deferens. J Pharmacol Exp Ther 227:199–204
Ohizumi Y, Yasumoto T (1983a) Contraction and increase in tissue calcium content induced by maitotoxin, the most potent known marine toxin, in intestinal smooth muscle. Br J Pharmacol 79:3–5
Ohizumi Y, Yasumoto T (1983b) Contractile response of the rababit aorta to maitotoxin, the most potent marine troxin. J Physiol 337:711–721
Stanfield PR (1970) The effect of the tetraethylammonium ion on the delayed current of frog skeletal muscle. J Physiol 209: 209–229
Sutko JL, Willerson JT (1980) Ryanodine alteration of the contractile state of rat ventricular myocardium. Comparison with dog, cat, and rabbit ventricular tissues. Circ Res 46:332–343
Takahashi M, Ohizumi Y, Yasumoto T (1982) Maitotoxin, a Ca2+ channel activator candidate. J Biol Chem. 257:7287–7289
Takahashi M, Tatsumi M, Ohizumi Y, Yasumoto T (1983) Ca2+ channel activating function of maitotoxin, the most potent marine toxin known, in clonal rat pheochromocytoma cells. J Biol Chem. 258:10944–10949
Washio H (1972) The ionic requirements for the initiation of action potentials in insect muscle fibres. J Gen Physiol 59: 121–134
Yamamoto D, Fukami J, Washio H (1981) Voltage clamp studies on insect skeletal muscle. I. The inward current. J Exp Biol 92:1–12
Yamamoto D, Washio H (1981) Voltage clamp studies on insect skeletal muscle. II. Outward current. J Exp Biol 92:13–22
Yasumoto T (1980) Ciguatera. Igaku no Ayumi 112:886–892 (in Japanese)
Yasumoto T, Nakajima I, Oshima Y, Bagnis R (1979) A new toxic dinoflagellate found in association with ciguatera. In: Taylor DL, Seliger H (eds) Toxic Dinoflagellate Blooms. Elsevier North Holland Inc, New York, pp 65–70
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Miyamoto, T., Ohizumi, Y., Washio, H. et al. Potent excitatory effect of maitotoxin on Ca channels in the insect skeletal muscle. Pflugers Arch. 400, 439–441 (1984). https://doi.org/10.1007/BF00587546
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00587546