The role of Ca2+-dependent cationic current in generating gamma frequency rhythmic bursts: modeling study
Section snippets
Experimental procedures
Our model of the FRB neuron has a single compartment, in which only ionic currents essential to generate FRBs are included. The membrane potential V obeys the current–balance equation where the membrane capacitance Cm=1 μF/cm2 and Iapp is an applied current. The leak current is given by Ileak=gleak(V−Eleak) with gleak=0.13 mS/cm2 and Eleak=−68.8 mV. The permeability ratio for the leak current is PK:PNa:PCl=1:0.04:0.45. The voltage-dependent currents INa, IK
Generation of hump-like DAPs and epileptiform bursts
In response to a short current pulse, the model neuron displays an action potential followed by a hump-like DAP (Fig. 2A). This DAP is similar to those seen in the previous electrophysiological studies (Kang and Kayano, 1994, Gray and McCormick, 1996, Brumberg et al., 2000, Kang, 1997, Haj-Dahmane and Andrade, 1997). The amplitude or the peak level of the DAP is determined independently by the following three parameters: the reversal potential for Icat (Ecat), the maximum conductance (gcat) and
INaP-based model vs. Icat-based model
A previous simulation study proposed that the gamma-band FRB was primarily generated, without Ca2+-activated channels, by a ‘ping-pong’ interplay between action potentials in the somatic compartment and INaP in the dendritic compartment (Wang, 1999). In such a two-compartment model neuron, the somatic action potential propagated backward into the dendrite to activate INaP, which in turn generated a DAP and led to the generation of bursts. The bursting pattern of the model neuron was determined
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific Research on Priority Areas (A) and by CREST (Core Research for Evolutional Science and Technology) of Japan Science and Technology (JST).
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