Cav1p3_MA2020_GoC#
- class braincell.channel.Cav1p3_MA2020_GoC(size, g_max=Quantity(5.e-06, '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 Cav1.3 L-type calcium current with Ca inactivation.
The Cav1.3 (L-type) calcium current of the cerebellar Golgi cell model of (Masoli et al., 2020) [3]. Its kinetics are the GENESIS Cav1.3 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:
\[\begin{split}\begin{aligned} I_{Ca} &= g_{max} \, m \, h \, n \, (E_{Ca} - V) \\ m_\infty &= \frac{1}{\exp(-(V' + 40) / 5) + 1} \\ \tau_m &= \frac{1}{\alpha_m + \beta_m} \\ \alpha_m &= \frac{39800 \times 15.005} {\mathrm{exprel}((V' + 67.24) / 15.005)} \\ \beta_m &= 3500 \exp(V' / 31.4) \\ h_\infty &= \frac{\mathrm{VDI}}{\exp((V' + 37) / 5) + 1} + (1 - \mathrm{VDI}) \\ \tau_h &= 44.3 \\ n_\infty &= \frac{k_f}{k_f + [Ca]_i / \mathrm{mM}} \\ \tau_n &= 0.5 \end{aligned}\end{split}\]where \(V' = V / \mathrm{mV}\), the time constants are in milliseconds, \(\mathrm{VDI} = 1.0\) and \(k_f = 0.0005\). Unlike
Cav1p2_MA2020_GoC(\(\mathrm{VDI} = 0.17\)), \(\mathrm{VDI} = 1.0\) here leaves no non-inactivating floor, so \(h_\infty\) reduces to the plain Boltzmann \(1 / (1 + \exp((V' + 37) / 5))\). The \(n\) gate is the imported mechanism’sh2state, a calcium-dependent inactivation with a fixed 0.5 ms time constant.\(\mathrm{exprel}(x) = (\exp(x) - 1) / x\), so \(\alpha_m\) equals the mod file’s literal \(39800 (V' + 67.24) / (\exp((V' + 67.24) / 15.005) - 1)\) while remaining finite at \(V' = -67.24\) mV, where the literal form is an indeterminate \(0/0\). At that voltage \(\mathrm{exprel}(0) = 1\) and \(\alpha_m = 39800 \times 15.005\), the limit of the mod file’s expression.
- 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 to0.000005 S/cm2, i.e.0.005 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 to0.0 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 to1.0, which makes the temperature scaling a no-op (see Notes).temp_ref (
Array|ndarray|bool|number|bool|int|float|complex|Quantity) – Reference temperature forq10. Defaults to 22 degrees Celsius.
See also
Cav1p2_MA2020_GoCSibling Cav1.2 current from the same import family and the same two origin papers; its
alpha_mkeeps the mod file’s literal, unguarded quotient.Cav1p3_MA2025_BCThe same mechanism re-imported for the basket cell model; identical kinetics, different model citation.
braincell.channel._base.OhmicHHTemplate supplying the ohmic driving force used above.
Notes
Ported from
GoC/channel/Cav1p3_MA20_GoC.mod. That file has noTITLE; 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]. 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
h2state 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_shis accepted, stored and never read: no rate method of this class uses it. That reproduces the mod file, whosePARAMETERblock likewise declaresvshift = 0 (mV)and never uses it. In the same spirit, the three gates are wired for Q10 scaling throughGate(q10="q10", temp_ref="temp_ref"), but the shipped defaults (q10 = 1.0andtemp = temp_ref = 22 degC) makephiexactly 1, matching the mod file, which applies no temperature scaling at all.Import deviation – rate-refresh relocation. The
rates()call moved fromBREAKPOINTintoDERIVATIVE state, soinf/tauare refreshed before thecnexpstate update rather than after it.Open question – a possible unit-scale defect inherited from upstream. The GENESIS original
CaL13CDI.gevaluates themTaulinoid in volts and returns seconds, whereas the NEURON port applies the same numeric coefficients in mV and declaresmTau (ms). Worked at \(V = 0\) mV, the GENESIS reading givestau_mabout 0.283 ms while the mod file – and hence this class – gives about 2.9e-5 ms, roughly 1e4 times smaller, i.e. effectively instantaneous activation. Cav1.2 shows the same pattern, and the transfer paper’s Methods mention no intentional rescaling. This 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
icahere isg * (v - eca), i.e. outward-positive;OhmicHHcomputesg_max * m h n * (E - V), the same current under BrainCell’s repo-wide inward-positive convention.g_max’s default is thegbarof the cell-model deposit this mechanism was imported from – a value tuned for that model, not a conductance reported by either origin paper.References