In the normal situation, tissue damage or inflammation leads to acute pain which ends after the tissue has healed. However, in some individuals, pain persists after healing, and thus is referred to as chronic pain. Recently, it was found that there is a relationship between the spontaneous firing rate of peripheral axons and the experience of chronic pain. This led us to the hypothesis that the pain system undergoes hysteresis during pain, and that chronic pain appears when a spontaneous relaxation mechanism fails. With this hypothesis in mind, a conceptual dynamic model of the pain system was developed using the newly developed neuron simulator ANNarchy. The anatomy and complexity of the model was chosen to be as simple as possible, while still satisfyingly exhibiting the expected behavior of a few established base cases. The model developed could successfully show how the increased spontaneous activity in the peripheral axons, caused by failing relaxation mechanisms, could hold the pain system in a dynamically stable excited state, and hence lead to chronic pain. Although this conceptual model is a very rough imitation of the pain system, the results suggests that it can be built upon to model dynamic characteristics of the hysteresis potentially involved in chronic pain.
