Kir2p3_RI2021_SC

class braincell.channel.Kir2p3_RI2021_SC(size, g_max=Quantity(0.9, 'mS / cm^2'), temp=Quantity(303.15, 'K'), name=None)

Kir2.3 inward-rectifier current of the stellate cell model.

Hyperpolarization-activated inward-rectifier potassium current imported from the cerebellar stellate cell model of Rizza et al. (2021) [2]. A single first-order d gate of power 1 drives an ohmic current, with the gate written in alpha/beta form:

\[\begin{split}\begin{aligned} \alpha_d &= 0.13289 \, \exp(-(V + 83.94) / 24.3902) \\ \beta_d &= 0.16994 \, \exp((V + 83.94) / 35.714) \end{aligned}\end{split}\]

where \(V\) is in millivolts and the rates are per millisecond. The template forms \(d_\infty = \alpha_d / (\alpha_d + \beta_d)\) and \(\tau_d = 1 / (\alpha_d + \beta_d)\) from these; half activation falls near -87.5 mV, and \(d_\infty\) rises towards 1 as the membrane hyperpolarizes. 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 0.9 mS/cm2, which is exactly the source mechanism’s gkbar = 0.0009 mho/cm2.

• temp (Array | ndarray | bool | number | bool | int | float | complex | Quantity) – Absolute temperature driving the gate’s q10 factor, default 30 degrees Celsius. This matches the celsius = 30 (degC) written in the source mechanism’s PARAMETER block.

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

See also

Kir2p3_MA2020_GrC

Granule-cell port of the same mechanism.

Kir2p3_MA2024_PC

Purkinje-cell port of the same mechanism.

Kir2p3_MA2025_BC

Basket-cell port of the same mechanism.

KM_RI2021_SC

M-type current of the same stellate model, sharing the same origin paper.

Notes

Ported from SC/channel/Kir2p3_RI21_SC.mod. That file and the granule, Purkinje and basket ports are byte-identical apart from their SUFFIX line and, in the Purkinje port only, the mechanism-local celsius default. The four BrainCell classes are likewise identical, so the rate constants above are shared verbatim with Kir2p3_MA2020_GrC, Kir2p3_MA2024_PC and Kir2p3_MA2025_BC. What differs is only the deposit each was imported from, and therefore the model paper cited below.

The rectification lives in the gate, not in the current. The current expression is the plain ohmic g_max * d * (E_K - V) supplied by OhmicHH; there is no Mg2+ or polyamine block term anywhere in the mechanism. The inward-rectifier behaviour comes entirely from \(d_\infty\) increasing as the membrane hyperpolarizes.

Where the q10 factor is applied. The gate declares q10 = 3.0 at a reference of 20 degrees Celsius, so HH.compute_derivative() scales the whole \(\alpha_d (1 - d) - \beta_d d\) term by \(\phi = 3^{(T - 20)/10}\), which is exactly 3 at the default 30 degrees Celsius. The .mod file instead multiplies Q10 into alp_d and bet_d. The two forms are algebraically identical, but it means f_d_alpha() and f_d_beta() return the q10-free rates rather than the mechanism’s alpha_d/beta_d.

Provenance, and what the header does not establish. The .mod COMMENT carries a reference string that is the published title of D’Angelo et al. (2001) truncated mid-subtitle, plus the porting note “Suffix from Ubc_Kir to Kir2_3”. Neither is treated as a citation here. The kinetics originate in the cerebellar granule cell model of D’Angelo et al. (2001) [1]; the stellate-cell paper [2] names the model this parameterisation was imported from, not the origin of the equations.

Conductance default. 0.9 mS/cm2 is the deposit’s tuned value, carried across from the .mod file. It is not a value printed in either cited paper.

Import deviations. The original mechanism’s NMODL TABLE over [-100, 100] mV, covering d_inf and tau_d, is not reproduced: both expressions are evaluated per call. NEURON used the boundary value outside that window, so any BrainCell-versus-NEURON divergence below -100 mV or above 100 mV is expected rather than a port error. The integration method was also changed from derivimplicit to cnexp; with one independent gate ODE that substitution is exact.

References

[1]

D’Angelo, E., Nieus, T., Maffei, A., Armano, S., Rossi, P., Taglietti, V., Fontana, A., & Naldi, G. (2001). Theta-frequency bursting and resonance in cerebellar granule cells: experimental evidence and modeling of a slow K+-dependent mechanism. The Journal of Neuroscience, 21(3), 759-770. doi:10.1523/JNEUROSCI.21-03-00759.2001

[2] (1,2)

Rizza, M. F., Locatelli, F., Masoli, S., Sanchez-Ponce, D., Munoz, A., Prestori, F., & D’Angelo, E. (2021). Stellate cell computational modeling predicts signal filtering in the molecular layer circuit of cerebellum. Scientific Reports, 11(1), 3873. doi:10.1038/s41598-021-83209-w

root_type

alias of Potassium