title: Post-stimulus hyperpolarization and slow potassium conductance increase in Aplysia giant neurone.
abstract: 1. Intracellular records from Aplysia giant (R2) cell somata showed long lasting 4-10 mV hyperpolarizations after passage of outward current through a second intracellular electrode.2. An increase in membrane slope conductance occurred simultaneously with the post-stimulus hyperpolarization (PSH).3. Both the PSH and conductance-increase varied strongly with stimulus amplitude and duration.4. Both the PSH and the conductance increase occurred in Ca-free medium containing tetrodotoxin, when action-potential production was completely blocked.5. The PSH persisted in the presence of ouabain or DNP, with cooling, with removal of external K(+), and in media where all the Na(+) was replaced with Li(+), suggesting that it was not due to the activity of an electrogenic pump.6. A reversal potential for the PSH was demonstrated by application of maintained inward current following the end of an outward-directed stimulus.7. The PSH reversal potential varied with [K](o), but not with [Cl](o) or [Na](o), suggesting that the PSH was mainly due to an increase in K conductance.8. The PSH and the conductance increase were reduced strongly when all the Na(+) was replaced with Tris, and only slightly when Na(+) was replaced with sucrose.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism; D004140:Dinitrophenols / Q000494:pharmacology; D008564:Membrane Potentials; D008974:Mollusca / Q000502:physiology*; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D002712:Chlorides; D004140:Dinitrophenols; D013779:Tetrodotoxin; D010042:Ouabain; D012964:Sodium; D011188:Potassium