Spontaneous and GABA-induced single channel currents in cultured murine spinal cord neurons.
Intracellular and patch clamp recordings were made from embryonic mouse spinal cord neurons growing in primary cell culture. Outside-out membrane patches obtained from these cells usually showed spontaneous single channel currents when studied at the resting potential (-56 +/- 1.5 mV). In 18 out of 30 patches tested, spontaneous single channel activity was abolished by making Tris+ the major cation on both sides of the membrane. The remaining patches continued to display spontaneous single channel currents under these conditions. These events reversed polarity at a patch potential of 0 mV and displayed a mean single channel conductance of 24 +/- 1.2 pS. Application of the putative inhibitory transmitter gamma-aminobutyric acid (0.5-10 microM) to outside-out patches of spinal cord cell membrane induced single channel currents in 10 out of 15 patches tested. These channels had a primary conductance of 29 +/- 2.8 pS in symmetrical 145 mM Cl- solutions. Frequency distributions for the open times of these channels were well fit by the sum of a fast exponential term ("of") with a time constant tau of = 4 +/- 1.3 ms and a slow exponential term ("os") with a time constant tau os = 24 +/- 8.1 ms. Frequency distributions for channel closed times were also well fit by a double exponential equation, with time constants tau cf = 2 +/- 0.2 ms and tau cs = 62 +/- 20.9 ms.
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D000818:Animals; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005260:Female; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D051379:Mice; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D012964:Sodium / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D007473:Ion Channels; D005680:gamma-Aminobutyric Acid; D012964:Sodium