Figure 5.

Illustrations of NCP expression at excitatory synapses on excitatory and inhibitory neurons in neuronal circuits of the SDH at physiological (left) and pathological (right) states. At physiological conditions, the circuits are in homeostatic states, and the activity of these types of excitatory synapses (indicated by red flashes) is stable. In pathological states (right panel), when the circuitry homeostasis is disrupted and NCP is expressed, excitatory inputs to inhibitory neurons are weakened, whereas excitatory inputs to excitatory neurons are strengthened. Consequently, the outputs (indicated by yellow flashes) of the inhibitory neurons are expected to decrease while the outputs of excitatory neurons increase. This form of circuitry plasticity will result in E/I imbalance and the expression of pathological pain.