Effects of 4-aminopyridine on calcium action potentials and calcium current under voltage clamp in spinal neurons.
We examined the effects of 4-aminopyridine (4-AP) on calcium conductance mechanisms in cultured mouse spinal cord neurons. At low concentrations (less than or equal to 1 mM), 4-AP enhanced Ca2+-dependent transmitter release and prolonged the duration of Ca2+-dependent action potentials. Voltage clamp studies indicated that 4-AP directly facilitates Ca2+ entry through voltage sensitive channels apart from an effect on K+ currents. These results may help to explain why the drug promotes Ca2+-dependent transmitter release at peripheral and central synapses.
D015761:4-Aminopyridine; D000200:Action Potentials / Q000187:drug effects; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D005333:Fetus; D051379:Mice; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D000631:Aminopyridines; D009467:Neuromuscular Depolarizing Agents; D013757:Tetraethylammonium Compounds; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D002118:Calcium