The code provided is a model for **transmitter release** at a synapse, a crucial biological process for signal transmission between neurons. This model is particularly centered around the kinetics of neurotransmitter release, without delving into the specifics of neurotransmitter type or target postsynaptic mechanisms. ### Biological Basis 1. **Synaptic Transmission:** - The **synaptic cleft** is the space between the presynaptic and postsynaptic neurons. Neurotransmitters released into the cleft enable the communication between these neurons. - **Transmitter release** typically occurs in response to an action potential reaching the presynaptic terminal, triggering the influx of calcium ions, which then prompt synaptic vesicles to fuse with the plasma membrane and release their content. 2. **Model Parameters:** - **Delay (`del`):** Represents the time after stimulation when neurotransmitter release begins. This can be interpreted as the synaptic delay, accounting for the sequence of events following an action potential. - **Duration (`dur`):** Indicates how long the transmitter release persists, reflecting the time course of neurotransmitter availability in the synaptic cleft. - **Amplitude (`amp`):** Denotes the concentration of neurotransmitter released, akin to the quantal content in synaptic vesicles and subsequent concentration profiles within the synaptic cleft. 3. **Key Aspects of the Model:** - **Timing Function:** Using `at_time()` suggests a temporal modulation, switching release on and off based on defined delays and durations, mimicking an action potential's effect on neurotransmitter release. - **Concentration (`T`):** The model computes a transmitter concentration at a point in time, which is a simplification of the dynamic diffusion and receptor-binding processes in an actual synaptic cleft. ### Scope and Simplification The model is a kinetic description, focusing on the timing and concentration dynamics of neurotransmitter release, abstracting away from calcium dynamics, vesicle fusion, and specific neurotransmitter-receptor interactions. By doing so, it aligns closely with models developed by Destexhe et al., as noted in the references, using a generalized kinetic formalism approach. In sum, this model captures the essentials of neurotransmitter release dynamics while simplifying many underlying biological complexities, making it a piece of broader models that integrate synaptic transmission into neuronal network simulations.