A fast transient outward current in the rat sympathetic neurone studied under voltage-clamp conditions.

摘要: Post-ganglionic neurones of the isolated rat superior cervical ganglion were voltage clamped at 37 degrees C using separate intracellular and current micro-electrodes. Control experiments in clamp suggested that neurone is electrotonically compact, soma proximal dendritic membranes being under good spatial uniformity. Depolarizing steps from membrane potentials near -50 mV evoked: (i) a voltage-dependent inward Na+ current, (ii) an Ca2+ (iii) outward K+ (iv) Ca2+-activated current. Depolarizations holding more negative than -60 elicited, besides currents mentioned above, fast transient IA which peaked 1-2.5 ms then decayed to zero following exponential time course. The was shown be primarily, if not exclusively, carried by K+. It unaffected removal external or addition Cd2+ weakly blocked tetraethylammonium ions partially 4-aminopyridine. showed linear instantaneous current-voltage relationship. Its activation ranged 0 with mid-point -30 mV. A conductance could described terms simple Boltzmann distribution for single gating particle valency +3. Both development inactivation followed course constant large resting potential (42 -70 mV) small (11 ms) -100 -40 Steady-state h infinity mV, -78 suggesting approximately 50% channels are available physiological potential. Action elicited various maximal repolarization rates dependent on itself. This dependence found reasonably agreement curve. These data consistent view sympathetic neurone, conditions, it rather delayed responsible action repolarization.