Voltage dependent sodium currents in cultured rat cerebellar granule cells

1990 ◽  
Vol 10 (5) ◽  
pp. 445-453 ◽  
Author(s):  
Fan Lin ◽  
Oscar Moran
Keyword(s):  
Steady State ◽  
Sodium Channels ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Inactivation Kinetics ◽  
Sodium Currents ◽  
Patch Clamp Technique ◽  
Cerebellar Granule ◽  
Voltage Dependent ◽  
Peak Value

Sodium currents were studied in granule cells dissociated from rat cerebellum. Macroscopic currents were recorded using the patch-clamp technique. Sudium currents, which are TTX sensitive, reached a maximum peak value of 0.42±0.08 pA/μm2 at 18.4±2.2 mV (n=6). Activation and inactivation kinetics and steady-state properties were described in terms of Hodgkin and Huxley, parameters. The properties of sodium channels in cultured rat cerebellar granule cells are very similar to those reported for various neural preparations.

Topiramate attenuates voltage-gated sodium currents in rat cerebellar granule cells

1997 ◽  
Vol 231 (3) ◽  
pp. 123-126 ◽  
Author(s):  
Cristina Zona ◽  
Maria Teresa Ciotti ◽  
Massimo Avoli
Keyword(s):  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Sodium Currents ◽  
Cerebellar Granule ◽  
Voltage Gated

Appearance of a fast inactivating voltage-dependent K+ currents in developing cerebellar granule cells in vitro

1997 ◽  
Vol 29 (4) ◽  
pp. 291-301 ◽  
Author(s):  
Yoshihiko Wakazono ◽  
Takashi Kurahashi ◽  
Kensuke Nakahira ◽  
Isao Nagata ◽  
Chitoshi Takayama ◽  
...  
Keyword(s):  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Cerebellar Granule ◽  
Voltage Dependent ◽  
K Currents

Silent Synapses in Developing Cerebellar Granule Neurons

2002 ◽  
Vol 87 (3) ◽  
pp. 1263-1270 ◽  
Author(s):  
Gabriele Losi ◽  
Kate Prybylowski ◽  
ZhanYan Fu ◽  
Jian Hong Luo ◽  
Stefano Vicini
Keyword(s):  
Ampa Receptors ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Glutamate Release ◽  
Long Term Potentiation ◽  
Patch Clamp Technique ◽  
Physiological Concentration ◽  
Cerebellar Granule ◽  
Silent Synapses ◽  
Term Potentiation

Silent synapses are excitatory synapses endowed exclusively with N-methyl-d-aspartate (NMDA) responses that have been proposed to acquire α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) responses during development and after long-term potentiation (LTP). These synapses are functionally silent because of the Mg2+ block of NMDA receptors at resting potentials. Here we provide evidence for the presence of silent synapses in developing cerebellar granule cells. Using the patch-clamp technique in the whole-cell configuration, we recorded the spontaneous excitatory postsynaptic currents (sEPSCs) from rat cerebellar granule cells in culture and in slices at physiological concentration of Mg2+ (1 mM). A holding potential of +60 mV removes Mg2+ block of NMDA channels, allowing us to record NMDA-sEPSCs. We thus compared the frequency of AMPA-sEPSCs, recorded at −60 mV, with that of NMDA-sEPSCs, recorded at +60 mV. NMDA-sEPSCs occurred at higher frequency than the AMPA-sEPSCs in most cells recorded in slices from rats at postnatal day (P) <13 and in culture at 6–8 days after plating (DIV6–8). In a few cells from young rats (P6–9) and in most neurons in culture at DIV6 we recorded exclusively NMDA-sEPSCs, supporting the hypothesis of existence of functional synapses with NMDA and without AMPA receptors. Increasing glutamate release in the slice with cyclothiazide and temperature increased AMPA and NMDA-sEPSCs frequencies but failed to alter the relative ratio of frequency of occurrence. Frequency ratio of NMDA versus AMPA-sEPSCs in slices was correlated with the weighted time constant of decay (τ w ) of NMDA-sEPSCs and decreased with development along the reported decrease of τ w . We suggest that the prevalence of synaptic NR2A subunits that confer faster kinetics is paralleled by the disappearance of silent synapses early in cerebellar development.

scholarly journals Effects of magnesium on inactivation of the voltage-gated calcium current in cardiac myocytes.

1989 ◽  
Vol 94 (4) ◽  
pp. 745-767 ◽  
Author(s):  
H C Hartzell ◽  
R E White
Keyword(s):  
Steady State ◽  
Ventricular Myocytes ◽  
Internal Surface ◽  
State Level ◽  
Inactivation Kinetics ◽  
Ca Channel ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Current Voltage ◽  
Voltage Dependent

The effects of changes in intracellular and extracellular free ionized [Mg2+] on inactivation of ICa and IBa in isolated ventricular myocytes of the frog were investigated using the whole-cell configuration of the patch-clamp technique. Intracellular [Mg2+] was varied by internal perfusion with solutions having different calculated free [Mg2+]. Increasing [Mg2+]i from 0.3 mM to 3.0 mM caused a 16% reduction in peak ICa amplitude and a 36% reduction in peak IBa amplitude, shifted the current-voltage relationship and the inactivation curve approximately 10 mV to the left, decreased relief from inactivation, and caused a dramatic increase in the rate of inactivation of IBa. The shifts in the current-voltage and inactivation curves were attributed to screening of internal surface charge by Mg2+. The increased rate of inactivation of IBa was due to an increase in both the steady-state level of inactivation as well as an increase in the rate of inactivation, as measured by two-pulse inactivation protocols. Increasing external [Mg2+] decreased IBa amplitude and shifted the current-voltage and inactivation curves to the right, but, in contrast to the effect of internal Mg2+, had little effect on the inactivation kinetics or the steady-state inactivation of IBa at potentials positive to 0 mV. These observations suggest that the Ca channel can be blocked quite rapidly by external Mg2+, whereas the block by [Mg2+]i is time and voltage dependent. We propose that inactivation of Ca channels can occur by both calcium-dependent and purely voltage-dependent mechanisms, and that a component of voltage-dependent inactivation can be modulated by changes in cytoplasmic Mg2+.

Ionic Mechanism of Electroresponsiveness in Cerebellar Granule Cells Implicates the Action of a Persistent Sodium Current

1998 ◽  
Vol 80 (2) ◽  
pp. 493-503 ◽  
Author(s):  
Egidio D'Angelo ◽  
Giovanna De Filippi ◽  
Paola Rossi ◽  
Vanni Taglietti
Keyword(s):  
Action Potential ◽  
Granule Cell ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Sodium Current ◽  
Ionic Mechanism ◽  
Persistent Sodium Current ◽  
Spike Discharge ◽  
Cerebellar Granule ◽  
Voltage Dependent

D'Angelo, Egidio, Giovanna De Filippi, Paola Rossi, and Vanni Taglietti. Ionic mechanism of electroresponsiveness in cerebellar granule cells implicates the action of a persistent sodium current. J. Neurophysiol. 80: 493–503, 1998. Although substantial knowledge has been accumulated on cerebellar granule cell voltage-dependent currents, their role in regulating electroresponsiveness has remained speculative. In this paper, we have used patch-clamp recording techniques in acute slice preparations to investigate the ionic basis of electroresponsiveness of rat cerebellar granule cells at a mature developmental stage. The granule cell generated a Na+-dependent spike discharge resistant to voltage and time inactivation, showing a linear frequency increase with injected currents. Action potentials arose when subthreshold depolarizing potentials, which were driven by a persistent Na+ current, reached a critical threshold. The stability and linearity of the repetitive discharge was based on a complex mechanism involving a N-type Ca2+ current blocked by ω-CTx GVIA, and a Ca2+-dependent K+ current blocked by charibdotoxin and low tetraethylammonium (TEA; <1 mM); a voltage-dependent Ca2+-independent K+ current blocked by high TEA (>1 mM); and an A current blocked by 2 mM 4-aminopyridine. Weakening TEA-sensitive K+ currents switched the granule cell into a bursting mode sustained by the persistent Na+ current. A dynamic model is proposed in which the Na+ current-dependent action potential causes secondary Ca2+ current activation and feedback voltage- and Ca2+-dependent afterhyperpolarization. The afterhyperpolarization reprimes the channels inactivated in the spike, preventing adaptation and bursting and controlling the duration of the interspike interval and firing frequency. This result reveals complex dynamics behind repetitive spike discharge and suggests that a persistent Na+ current plays an important role in action potential initiation and in the regulation of mossy fiber-granule cells transmission.

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