Tetrodotoxin: effects on brain metabolism in vitro.

A 3-micromolar concentration of tetrodotoxin completely inhibits the stimulation of respiration of rat brain cortex that takes place upon application of electrical impulses. It also inhibits increase in the rate of the respiration that occurs when calcium ions are omitted from the incubation medium. No effect of tetrodotoxin on brain respiration takes place when stimulation is brought about by the addition of 100 millimolar potassium chloride. Tetrodotoxin prevents the fall in the rate of oxidation of cerebral acetate that occurs during electrical stimulation but does not affect the increased rate of the oxidation that occurs in the presence of an increased concentration of potassium chloride. The data indicate that oxidation of cerebral acetate is diminished by influx of sodium ions, which is prevented by tetrodotoxin, and is increased by influx of potassium ions, which is unaffected by tetrodotoxin.