Can an increase in neuropeptide production in the soma lead to DCV circulation in axon terminals with type III en passant boutons?

- Effects of increased DCV production rate in the neuron soma are investigated.
- If DCV production increases, DCV circulation in type III terminals may develop.
- DCV circulation in type III terminals gets stronger when DCV production increases.
- In type III boutons it takes some time before the circulation appears.
- An increase in DCV production also increases DCV circulation in type Ib terminals.

Neuropeptides are synthesized in the neuron soma; they are packaged in dense core vesicles (DCVs) which undergo axonal transport toward nerve terminals. Published experimental results suggest that in terminals with type Ib boutons DCVs circulate in the terminal, undergoing repeated anterograde and retrograde transport, while in type III terminals DCVs do not circulate in the terminal. In this paper we developed a mathematical model that allowed us to investigate the effects of an increased rate of DCV production in the soma. We demonstrated that our model reproduces some important experimental results, in particular those concerning DCV circulation in type Ib and type III terminals. Our model makes testable predictions. Probably the most important prediction concerns the effect of an increased DCV production rate in the soma, which we anticipate leads to increased DCV circulation in type Ib boutons and to the appearance of DCV circulation in type III boutons. Other predictions concern various stages of development of DCV circulation in the terminals after they were depleted of DCVs due to neuropeptide release.

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