GABAa

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GABAa#

class brainpy.state.GABAa(in_size, name=None, alpha=Quantity(0.53, "1 / (mM * ms)"), beta=Quantity(0.18, "kHz"), T=Quantity(1., "mM"), T_dur=Quantity(1., "ms"), g_initializer=Constant(value=0. mS))#

GABAa receptor synapse model.

This class implements a kinetic model of GABAa (gamma-aminobutyric acid type A) receptor-mediated synaptic transmission. GABAa receptors are ionotropic chloride channels that mediate fast inhibitory synaptic transmission in the central nervous system.

The model uses the same Markov process approach as the AMPA model but with different kinetic parameters appropriate for GABAa receptors:

\[ \frac{dg}{dt} = \alpha [T] (1-g) - \beta g \]

\[ I_{syn} = - g_{max} \cdot g \cdot (V - E) \]

where:

  • \(g\) represents the fraction of receptors in the open state

  • \(\alpha\) is the binding rate constant [ms^-1 mM^-1], typically slower than AMPA

  • \(\beta\) is the unbinding rate constant [ms^-1]

  • \([T]\) is the neurotransmitter (GABA) concentration [mM]

  • \(I_{syn}\) is the resulting synaptic current (note the negative sign indicating inhibition)

  • \(g_{max}\) is the maximum conductance

  • \(V\) is the membrane potential

  • \(E\) is the reversal potential (typically around -80 mV for chloride)

The neurotransmitter concentration \([T]\) follows a square pulse of amplitude T and duration T_dur after each presynaptic spike.

Parameters:

  • in_size (Size) – Size of the input.

  • name (str, optional) – Name of the synapse instance.

  • alpha (ArrayLike, default 0.53/(u.ms*u.mM)) – Binding rate constant [ms^-1 mM^-1]. Typically slower than AMPA receptors.

  • beta (ArrayLike, default 0.18/u.ms) – Unbinding rate constant [ms^-1].

  • T (ArrayLike, default 1.0*u.mM) – Peak neurotransmitter concentration when released [mM]. Higher than AMPA.

  • T_dur (ArrayLike, default 1.0*u.ms) – Duration of neurotransmitter presence in the synaptic cleft [ms]. Longer than AMPA.

  • g_initializer (ArrayLike or Callable, default init.Constant(0. * u.mS)) – Initial value or initializer for the synaptic conductance.

Inherits all attributes from AMPA class.

See also

AMPA

Excitatory AMPA receptor synapse model.

BioNMDA

NMDA receptor synapse model.

Notes

  • GABAa receptors typically produce slower-rising and longer-lasting currents compared to AMPA receptors [1].

  • The inhibitory nature of GABAa receptors is reflected in the convention of using a negative sign in the synaptic current equation.

  • The reversal potential for GABAa receptors is typically around -80 mV (due to chloride), making them inhibitory for neurons with resting potentials more positive than this value.

  • This model does not include desensitization, which can be significant for prolonged GABA exposure [2].

References

Examples

>>> import brainpy
>>> import brainstate
>>> import saiunit as u
>>> # Create a GABAa synapse
>>> gabaa = brainpy.state.GABAa(100)
>>> gabaa.init_state(batch_size=1)
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