Modeling neuropeptide transport in various types of nerve terminals containing en passant boutons

• A compartmental model that simulates DCV transport in nerve terminals is developed.
• The difference in DCV number in type Ib and type III terminals is explained.
• There is a DCV circulation in type Ib nerve terminals.
• There is no such circulation in type III terminals.
• In type Ib terminals with DIMM there is also a weak DCV circulation.

We developed a mathematical model for simulating neuropeptide transport inside dense core vesicles (DCVs) in axon terminals containing en passant boutons. The motivation for this research is a recent experimental study by Levitan and colleagues (Bulgari et al., 2014) which described DCV transport in nerve terminals of type Ib and type III as well as in nerve terminals of type Ib with the transcription factor DIMM. The goal of our modeling is validating the proposition put forward by Levitan and colleagues that the dramatic difference in DCV number in type Ib and type III terminals can be explained by the difference in DCV capture in type Ib and type III boutons rather than by differences in DCV anterograde transport and half-life of resident DCVs. The developed model provides a tool for studying the dynamics of DCV transport in various types of nerve terminals. The model is also an important step in gaining a better mechanistic understanding of transport processes in axons and identifying directions for the development of new models in this area.

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