TETRODOTOXIN ON SODIUM AND OTHER IONS OF CEREBRAL TISSUES EXCITED ELECTRICALLY AND WITH GLUTAMATE

Abstract— Guinea pig neocortical tissues incubated in glucose‐bicarbonate salines maintained defined intracellular Na concentrations which were about 0.25 those of the salines and were unaffected by tetrodotoxin. Electrical stimulation or the addition of 5 mm‐l‐glutamic acid allowed tissue Na to increase at about 400,μequiv./g hr. Tetrodotoxin almost completely prevented the increase induced electrically, and partly inhibited that induced by glutamate. Influx of 22Na induced by glutamate was also partly inhibited by the toxin. The extrusion of Na following electrical excitation was unaffected by tetrodotoxin. The concentration of tetrodotoxin needed for half‐maximal inhibition of Na movement induced electrically, was 25–30 mμm. Action of the toxin was reversed by washing the tissue, and the tetrodotoxin associated with the tissue during its action was probably no more than 0 15 mμmoles/g tissue. Structurala factors common to the molecules of tetrodotoxin, glutamic acid and membrane components considered to be involved in cation movements, are indicated. Copyright © 1969, Wiley Blackwell. All rights reserved