Kv2p2_0010_MA2020_GrC

Kv2p2_0010_MA2020_GrC#

class braincell.channel.Kv2p2_0010_MA2020_GrC(size, g_max=Quantity(0.01, 'mS / cm^2'), BBiD=10.0, name=None)#

Kv2.2 delayed-rectifier current of the granule cell model.

Slowly inactivating delayed-rectifier potassium current attributed to Kv2.2, imported from the cerebellar granule cell model of Masoli et al. (2020) [3]. Two first-order gates of power 1, an activation m and an inactivation h, drive an ohmic current:

\[\begin{split}\begin{aligned} m_\infty &= \frac{1}{1 + \exp(-(V - 5) / 12)} \\ \tau_m &= \frac{130}{1 + \exp(-(V + 46.56) / 44.14)} \\ h_\infty &= \frac{1}{1 + \exp((V + 16.3) / 4.8)} \\ \tau_h &= \frac{10000}{1 + \exp(-(V + 46.56) / 44.14)} \end{aligned}\end{split}\]

where \(V\) is in millivolts and both time constants are in milliseconds. The two time constants share a denominator and differ only by a factor of about 77, so inactivation is very slow – \(\tau_h\) approaches 10 seconds at depolarized potentials. This class applies no voltage shift, and the reversal potential comes from the potassium ion object rather than from the class.

Parameters:

  • size (int | Sequence[int] | integer | Sequence[integer]) – Channel state shape.

  • g_max (Array | ndarray | bool | number | bool | int | float | complex | Quantity | Callable) – Maximal conductance density. Defaults to 0.01 mS/cm2, which is exactly the source mechanism’s gKv2_2bar = 0.00001 S/cm2.

  • BBiD (Array | ndarray | bool | number | bool | int | float | complex | Quantity | Callable) – Channelpedia ion-channel identifier, default 10.0 (dimensionless). This is inert metadata, not a kinetic parameter; see the note below.

  • name (str | None) – Optional channel name.

See also

Kir2p3_MA2020_GrC

Inward rectifier of the same granule cell model.

KM_MA2020_GrC

M-type current of the same granule cell model.

Notes

Ported from GrC/channel/Kv2p2_0010_MA20_GrC.mod.

No temperature dependence. Neither gate declares phi or q10, so HH.gate_phi() resolves to 1.0, and the class takes no temp parameter at all. This is faithful: the .mod file contains no celsius reference and no Q10 term.

``BBiD`` is metadata, not a parameter of the model. In the .mod file BBiD = 10 is declared RANGE but never appears in any equation, and BrainCell likewise stores it and never reads it. It is the Channelpedia identifier for Kv2.2 (gene KCNB2), and it is also the 0010 embedded in the class name.

How this mechanism was produced. The .mod file is machine generated, not hand written: its version-control keywords name the EPFL Blue Brain xmlTomod/CreateMOD.c generator behind the Channelpedia database of Ranjan et al. (2011) [2]. That record is cited here for the toolchain and the channel identity only – it is not the source of the rate constants above. Those come from the delayed-rectifier component identified in gastrointestinal smooth muscle by Schmalz et al. (1998) [1], which the .mod header’s own :Reference : line names. The granule-cell paper [3] names the model this parameterisation was imported from; the companion Golgi-cell paper of the same year covers a different deposit and is not cited here.

Conductance default. 0.01 mS/cm2 is the deposit’s tuned value, carried across from the .mod file. It is not a value printed in any of the cited papers.

Import deviations: none. This mechanism carries no NMODL TABLE and was already integrated with cnexp upstream. Its rate block is wrapped in UNITSOFF/UNITSON, which BrainCell reproduces by evaluating the expressions on the dimensionless millivolt value of V.

References

root_type#

alias of Potassium