Fast pseudo-periodic oscillation in the rat brain voltage-gated sodium channel alpha subunit.
In the work reported here, we have investigated the changes in the activation and fast inactivation properties of the rat brain voltage-gated sodium channel (rNa(v) 1.2a) alpha subunit, expressed heterologously in the Chinese Hamster Ovary (CHO) cells, by short depolarizing prepulses (10-1000 ms). The time constant of recovery from fast inactivation (tau(fast)) and steady-state parameters for activation and inactivation varied in a pseudo-oscillatory fashion with the duration and amplitude of a sustained prepulse. A consistent oscillation was observed in most of the steady-state and non-inactivating current parameters with a time period close to 225 ms, although a faster oscillation of time period 125 ms was observed in the tau(fast). The studies on the non-inactivating current and steady-state activation indicate that the phase of oscillation varies from cell to cell. Co-expression of the beta1 subunit with the alpha subunit channel suppressed the oscillation in the charge movement per single channel and free energy of steady-state inactivation, although the oscillation in the half steady-state inactivation potential remained unaltered. Incidentally, the frequencies of oscillation in the sodium channel parameters (4-8 Hz) correspond to the theta component of network oscillation. This fast pseudo-oscillatory mechanism, together with the slow pseudo-oscillatory mechanism found in these channels earlier, may contribute to the oscillations in the firing properties observed in various neuronal subtypes and many pathological conditions.
Majumdar
S
S
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
Sikdar
S K
SK
D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000502:physiology; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004827:Epilepsy / Q000378:metabolism / Q000503:physiopathology; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; D018408:Patch-Clamp Techniques; D051381:Rats; D012964:Sodium / Q000378:metabolism* / Q000502:physiology; D015222:Sodium Channels / Q000378:metabolism* / Q000502:physiology
D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; C568253:Scn2A protein, rat; D015222:Sodium Channels; D012964:Sodium