A Computational Model to Investigate GABA-Activated Astrocyte Modulation of Neuronal Excitation

Figure 4

The dynamic response of astrocyte to presynaptic glutamate and exogenous GABA. (a) The amount of presynaptically released glutamate (Glu_syn) decreases as the concentration of exogenous GABA increases, but (b) there is greater activation of mGluRs on astrocyte due to the crosstalk with GABA_B receptors, which results in (c) IP₃ production and (d) IP₃-gated [Ca²⁺] elevation. (e) Once the [Ca²⁺] threshold has been reached (0.2 μM, red dashed line), astrocyte releases glutamate (Glu_astro) into the extracellular space. To avoid triggering repeatedly the release in all the time steps, gliotransmitter release event is triggered only once in threshold conditions, a mechanism similar to the refractory period of the neuron.