The provided code simulates NMDA receptor dynamics in neuronal systems using a model that includes a magnesium (Mg2+) block. NMDA receptors are a subtype of glutamate receptors found in the brain and play a crucial role in synaptic plasticity, learning, and memory.
Glutamate and Binding: The NMDA receptors are activated by the binding of glutamate, a key excitatory neurotransmitter, to the receptor. The parameter Alpha represents the forward binding rate of glutamate to the receptor, while Beta represents the backward, or unbinding, rate.
Conductance and Current: The code models the receptor conductance (g_eff) and the resulting synaptic current (i). The conductance changes as channels open or close, depending on glutamate binding and the influence of voltage-dependent mechanisms.
mag, eta, and gamma. At resting membrane potentials, Mg2+ ions block the NMDA channels. When the postsynaptic cell depolarizes, the block is removed, allowing Na+ and Ca2+ ions to flow through.Short Transmitter Pulses: The model simulates short pulses of neurotransmitter release, with a parameter Cdur indicating the duration of the neurotransmitter release event (rise phase). This aligns with the synaptic events where neurotransmitter release occurs rapidly upon presynaptic neuronal firing.
Channel Dynamics: The variables Ron and Roff represent the states of the channel (bound/open and unbound/closed, respectively). The differential equations are used to model the first-order kinetics of the receptor's state transitions.
The code models NMDA receptor-mediated synaptic conductance, accounting for critical biological features such as ligand binding, Mg2+ voltage-dependent block, and the receptor's role in Ca2+ influx. The ability of the receptor to integrate both chemical signals (glutamate binding) and electrical signals (membrane potential changes) plays a crucial role in neuronal communication and plasticity.