The effects of increased extracellular potassium in the isolated spinal cord on the flexor reflex of the frog.

The effects of superfusing the isolated frog spinal cord with various concentrations of K+ on flexor reflexes were examined. The reflexes were evoked by pinching or by electrical stimulation. An increase in [K+]e from 2 to 6 mmol/l facilitates the flexor reflex. Higher [K+]e produces inhibition. It is suggested that the increase in [K+]e which may occur under physiological conditions facilitates the impulse transmission, and that larger increases in [K+]e which likely occur only under extreme conditions, result in inhibition.