scholarly journals Sodium currents and sodium-current fluctuations in rat myelinated nerve fibres

1982 ◽  
Vol 329 (1) ◽  
pp. 163-184 ◽  
Author(s):  
B. Neumcke ◽  
R. Stämpfli
Keyword(s):  
Sodium Current ◽  
Current Fluctuations ◽  
Sodium Currents ◽  
Nerve Fibres ◽  
Myelinated Nerve

Sodium Currents in Neurons From the Rostroventrolateral Medulla of the Rat

2003 ◽  
Vol 90 (3) ◽  
pp. 1635-1642 ◽  
Author(s):  
Ilya A. Rybak ◽  
Krzysztof Ptak ◽  
Natalia A. Shevtsova ◽  
Donald R. McCrimmon
Keyword(s):  
Sodium Channels ◽  
Sodium Current ◽  
Cell Voltage ◽  
Kinetic Properties ◽  
Persistent Sodium Current ◽  
Sodium Currents ◽  
Bötzinger Complex ◽  
Window Current ◽  
Bursting Activity

Rapidly inactivating and persistent sodium currents have been characterized in acutely dissociated neurons from the area of rostroventrolateral medulla that included the pre-Bötzinger Complex. As demonstrated in many studies in vitro, this area can generate endogenous rhythmic bursting activity. Experiments were performed on neonate and young rats (P1-15). Neurons were investigated using the whole cell voltage-clamp technique. Standard activation and inactivation protocols were used to characterize the steady-state and kinetic properties of the rapidly inactivating sodium current. Slow depolarizing ramp protocols were used to characterize the noninactivating sodium current. The “window” component of the rapidly inactivating sodium current was calculated using mathematical modeling. The persistent sodium current was revealed by subtraction of the window current from the total noninactivating sodium current. Our results provide evidence of the presence of persistent sodium currents in neurons of the rat rostroventrolateral medulla and determine voltage-gated characteristics of activation and inactivation of rapidly inactivating and persistent sodium channels in these neurons.

Differences in voltage-dependent sodium currents exhibited by superficial and deep layer neurons of guinea pig entorhinal cortex

1994 ◽  
Vol 71 (5) ◽  
pp. 1986-1991 ◽  
Author(s):  
S. Fan ◽  
M. Stewart ◽  
R. K. Wong
Keyword(s):  
Guinea Pig ◽  
Entorhinal Cortex ◽  
Deep Layer ◽  
Sodium Current ◽  
Membrane Conductance ◽  
Cell Voltage ◽  
Superficial Layer ◽  
Peak Amplitude ◽  
Sodium Currents ◽  
Test Pulse

1. Sodium currents were studied using whole-cell voltage-clamp techniques in neurons acutely isolated from superficial (II/III) and deep (V/VI) layers of guinea pig entorhinal cortex. 2. Sodium currents were larger (peak amplitude) in superficial than in deep layer cells under the same conditions: -1939 +/- 780 (SD) pA (N = 6) versus -307 +/- 257 pA (N = 6). Specific membrane conductance was calculated to be 12.3 +/- 9.6 mS/cm2 for superficial layer cells and 1.4 +/- 0.9 mS/cm2 for deep layer cells. 3. Sodium currents could be activated in superficial layer cells from potentials as depolarized as -20 mV, whereas no significant currents could be activated in deep neurons from potentials more depolarized than about -50 mV. Using a protocol consisting of a 25-ms prepulse and a 20 ms test pulse, the inactivation curves for superficial layer cells were found to be shifted toward more depolarized potentials by an average of 15 mV (V50 = -59.8 +/- 3.8 mV compared with -75.7 +/- 12.0 mV for deep cells). This produced a region of overlap with the activation curves for superficial cells. 4. Over a range of about -50 to -20 mV in superficial layer cells, the region of overlap of the activation and inactivation curves, a sodium current could be activated, which did not fully inactivate during the test pulse (average peak amplitude: -89.5 +/- 48.7 pA; crossover voltage: -39.2 +/- 2.0 mV). Voltage steps to more depolarized potentials, outside the voltage “window”, permitted complete inactivation of the sodium current.(ABSTRACT TRUNCATED AT 250 WORDS)

Sign in / Sign up

Export Citation Format

Share Document