title: A late slow depolarization unmasked in the presence of tetraethylammonium in neonatal rat sympathetic neurons in vitro.
abstract: Neonatal rat superior cervical ganglia were mechanically dissociated, and the sympathetic neurons grown in dispersed cell cultures. Intracellular microelectrodes were used to study the effects of tetraethylammonium (TEA+), a blocker of outward K+ currents, on the excitable properties of these neurons. Addition of TEA+ to the perfusion media (TEA+-media) caused the resting potential to depolarize and the action potential to increase in duration. In TEA+-media (20-60 mM), a late delayed depolarization (LDD) followed the falling phase of the action potential with a delay of 1.5-2 s (n = 95). The LDD peak amplitude was in the range of 4-26 mV and the duration, to full return of the resting potential, was in the range of 18-90 s. For a given cell the amplitude and duration of the LDD were constant. The LDD was associated with a conductance increase. No LDD could be elicited in the presence of calcium channel blockers. Evidence was found for a Ca2+-dependence of the LDD: increasing the extracellular Ca2+ concentration caused increases in the amplitude and duration of the LDD. The significance of an endogenous LDD-like potential and possible explanations for the origin of the LDD are discussed.
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000187:drug effects*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
chemical_list: D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D011188:Potassium; D002118:Calcium