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.
Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
S K
SK
Sikdar
P
P
Legendre
B
B
Dupouy
J D
JD
Vincent
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