Action potential fatigue in nonmyelinated nerve fibers: garfish olfactory and rabbit vagus nerve.
A decrease in amplitude and conduction speed in the compound action potential is observed with time in gar olfactory and rabbit vagus nerve when it is stimulated between 4 and 15 Hz at 26 degrees C in vitro. The amplitude decays exponentially for 1-3 min before reaching a steady state. Recs 15 s for gar olfactory nerve and 50 s for rabbit vagus nerve. The steady state values are 14% and 36% of the original amplitude, respectively, and conduction speeds are reduced by 25 % in both nerves. The effect results from completion between ion flow during the action potential and active transport. The accumulation of K+ions and depletion of Na+ ions in the restricted extracellular space contributes to the amplitude fatigue while the depletion of Na+ ions alone causes the decrease in conduction speed. Ouabain increases the fatigue rate in both preparations, but more so for gar. The fatigue and recovery measurements may provide a useful method to investigate active pumping, including both the total pumping rate and the electrogenic component.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D005399:Fishes / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D009832:Olfactory Nerve / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors; D014630:Vagus Nerve / Q000502:physiology*
D010042:Ouabain; D012964:Sodium; D011188:Potassium