Computational modeling of biological networks--specifically, signaling pathways--is increasingly seen by computer scientists as an interesting application. In this paper, the approach is applied to a significantly more complex system--the calyx of Held, a type of synapse (connection point between two neurons). Communication between the presynaptic and postsynaptic neurons is achieved by the release of neurotransmitters into the interneuronal space, which in turn is facilitated by the action of calcium on presynaptic vesicles. Biologists actively research the exact mechanism of calcium release and its local distribution.

Bracciali et al. take a well-known model of this system and simulate it via the stochastic Pi-calculus machine (SPiM), strengthening the view that a stochastic model is a more realistic model than the original deterministic one. The description of the model is clear and the authors show how it can be used to derive several properties, such as plasticity of the synapse. The simulation of various situations is illustrated clearly.

However, the paper does not examine in detail pressing research questions that such a model could address. Indeed, most of the related work cited in the paper is by computer scientists and not biologists--specifically, the application of 6-difluorophenoxyacetamide (PEPA), (mem)brane calculus, and the BioSPI Project. Are biologists really ready to wield formal notations and Petri dishes? But, this paper is clearly targeted to computer scientists and as such, does a very good job of explaining the approach.