Cav1p2_MA2020_GoC

Cav1p2_MA2020_GoC#

class braincell.channel.Cav1p2_MA2020_GoC(size, g_max=Quantity(0.0002, 'S / cm^2'), V_sh=Quantity(0., 'mV'), temp=Quantity(295.15, 'K'), q10=1.0, temp_ref=Quantity(295.15, 'K'), name=None)#

Golgi cell Cav1.2 L-type calcium current with Ca inactivation.

The Cav1.2 (L-type) calcium current of the cerebellar Golgi cell model of (Masoli et al., 2020) [3]. Its kinetics are the GENESIS Cav1.2 model of (Evans, Maniar & Blackwell, 2013) [1], transferred from GENESIS to NEURON by (Beining et al., 2017) [2]. Gating is \(m\,h\,n\) with an ohmic driving force:

\[\begin{split}\begin{aligned} I_{Ca} &= g_{max} \, m \, h \, n \, (E_{Ca} - V) \\ m_\infty &= \frac{1}{1 + \exp(-(V' + 8.9) / 6.7)} \\ \tau_m &= \frac{1}{\alpha_m + \beta_m} \\ \alpha_m &= \frac{39800 \, (V' + 8.124)} {\exp((V' + 8.124) / 9.005) - 1} \\ \beta_m &= 990 \exp(V' / 31.4) \\ h_\infty &= \frac{\mathrm{VDI}}{1 + \exp((V' + 55) / 8)} + (1 - \mathrm{VDI}) \\ \tau_h &= 44.3 \\ n_\infty &= \frac{k_f}{k_f + [Ca]_i / \mathrm{mM}} \\ \tau_n &= 0.5 \end{aligned}\end{split}\]

where \(V' = V / \mathrm{mV}\), the time constants are in milliseconds, \(\mathrm{VDI} = 0.17\) and \(k_f = 0.0005\). The \(n\) gate is the imported mechanism’s h2 state: a calcium-dependent inactivation whose steady state depends on the internal calcium concentration alone and which relaxes with a fixed 0.5 ms time constant. Because \(\mathrm{VDI} = 0.17\), the voltage-dependent inactivation \(h_\infty\) never falls below 0.83.

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 0.0002 S/cm2, i.e. 0.2 mS/cm2 (see Notes).

  • V_sh (Array | ndarray | bool | number | bool | int | float | complex | Quantity | Callable) – Threshold shift. Accepted and stored, but read by no rate method of this class (see Notes). Defaults to 0.0 mV.

  • temp (Array | ndarray | bool | number | bool | int | float | complex | Quantity) – Absolute temperature driving the gate Q10 factors. Defaults to 22 degrees Celsius.

  • q10 (Array | ndarray | bool | number | bool | int | float | complex | Quantity | Callable) – Q10 factor shared by all three gates. Defaults to 1.0, which makes the temperature scaling a no-op (see Notes).

  • temp_ref (Array | ndarray | bool | number | bool | int | float | complex | Quantity) – Reference temperature for q10. Defaults to 22 degrees Celsius.

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

See also

Cav1p3_MA2020_GoC

Sibling Cav1.3 current from the same import family and the same two origin papers, with its own Boltzmann parameters and an exprel-guarded tau_m.

Cav1p2_MA2025_BC

The same mechanism re-imported for the basket cell model; identical kinetics, different model citation.

braincell.channel._base.OhmicHH

Template supplying the ohmic driving force used above.

Notes

Ported from GoC/channel/Cav1p2_MA20_GoC.mod. That file has no TITLE; its whole header is the comment “model from Evans et al 2013, transferred from GENESIS to NEURON by Beining et al (2016), ‘A novel comprehensive and consistent electrophysiologcal model of dentate granule cells’” (typo in the original). Both fields that header gives are wrong: the transfer paper appeared in 2017, and the quoted title corresponds to no published paper or preprint – it reads as a pre-publication working title. The citable record is the 2017 eLife paper [2]. Note also that Evans et al. (2013) is a striatal medium spiny neuron paper, not a dentate granule cell paper, despite what the header’s phrasing invites.

The mod file’s second header line, “also added Calcium dependent inactivation”, and an inline comment crediting the h2 state to “santhakumar 05” are recorded here as prose only. The verified bibliography resolves this mechanism to the two origin papers cited above and does not resolve that third credit, so no reference entry is written for it.

V_sh is accepted, stored and never read: no rate method of this class uses it. That reproduces the mod file, whose PARAMETER block likewise declares vshift = 0 (mV) and never uses it. In the same spirit, the three gates are wired for Q10 scaling through Gate(q10="q10", temp_ref="temp_ref"), but the shipped defaults (q10 = 1.0 and temp = temp_ref = 22 degC) make phi exactly 1, matching the mod file, which applies no temperature scaling at all.

Import deviation – rate-refresh relocation. The rates() call moved from BREAKPOINT into DERIVATIVE state, so inf/tau are refreshed before the cnexp state update rather than after it.

Open question – a possible unit-scale defect inherited from upstream. The GENESIS originals (CaL12CDI.g, CaL13CDI.g) evaluate the mTau linoid in volts and return seconds, whereas the NEURON ports apply the same numeric coefficients in mV and declare mTau (ms). The worked comparison is given in Cav1p3_MA2020_GoC’s Notes, and Cav1.2 shows the same pattern. That comparison is derived arithmetic, not a fetched claim, and it was not confirmed against a NEURON run, so it is recorded as an open question rather than as a defect: BrainCell reproduces the mod file faithfully under either reading, and this docstring asserts neither.

NEURON’s raw ica here is g * (v - eca), i.e. outward-positive; OhmicHH computes g_max * m h n * (E - V), the same current under BrainCell’s repo-wide inward-positive convention.

g_max’s default is the gbar of the cell-model deposit this mechanism was imported from – a value tuned for that model, not a conductance reported by either origin paper.

References

root_type#

alias of Calcium