Maturation of a transient outward potassium current in mouse fetal hypothalamic neurons in culture.
The whole-cell voltage clamp technique was used to record potassium currents in mouse fetal hypothalamic neurons developing in culture medium from days 1 to 17. The neurons were derived from fetuses of IOPS/OF1 mice on the 14th day of gestation. The mature neurons (greater than six days in culture) showed both a transient potassium current and a non-inactivating delayed rectifier potassium current. These were identified pharmacologically by using the potassium channel blockers tetraethyl ammonium chloride and 4-aminopyridine, and on the basis of their kinetics and voltage sensitivities. The delayed rectifier potassium current had a threshold of-20 mV, a slow time-course of activation, and was sustained during the voltage pulse. The 4-aminopyridine-sensitive current was transient, and was activated from a holding potential more negative (-80 mV) than that required for evoking the delayed rectifier potassium current (-40 mV). The delayed rectifier potassium current was detectable from day 1 onwards, while the transient potassium current showed a distinct developmental trend. The time-constant of inactivation became faster with age in culture. The half steady-state inactivation potential showed a shift towards less negative membrane potentials with age, and the relationship was best described by a logarithmic regression equation. The developmental trend of the transient potassium current may relate functionally to the progressive morphological changes, and the appearance of synaptic connections during ontogenesis.
Sikdar
S K
SK
Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
Legendre
P
P
Dupouy
B
B
Vincent
J D
JD
D000818:Animals; D002478:Cells, Cultured; D004594:Electrophysiology; D005333:Fetus / Q000502:physiology*; D006706:Homeostasis; D007031:Hypothalamus / Q000166:cytology / Q000196:embryology*; D051379:Mice; D009474:Neurons / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D013997:Time Factors
D015221:Potassium Channels; D011188:Potassium