A drug that blocks ATP production is introduced into an isolated axon preparation. The axon is then repeatedly stimulated, and recordings are made of the response. What effects would you expect to observe?

Answer 1

Initially, the recording would show normal action potentials in response to the repetitive stimulation. After 50,000 to 100,000 action potentials have passed, the recording would start to indicate less responsiveness from the axon; ultimately, the axon would fail to respond. Because very few ions actually move across the membrane during an action potential, axons can carry thousands of action potentials before the concentrations of sodium and potassium ions must be reestablished by the sodium-potassium pump. Without ATP production, the supply of ATP would be consumed, the pump would shut down, and so the cell could not restore the sodium and potassium ion gradients. The resulting slow depolarization would inactivate voltage-gated sodium channels, leading to a persistent absolute refractory state. The loss of the electrochemical gradients denies the axons their means of generating an action potential and transmission would stop.