Our rat model of peripheral neuroinflammation is used to screen novel compounds against tactile and thermal allodynia. In this model, neuroinflammation and neuropathic pain can be induced unilaterally using complete Freud’s adjuvant (CFA). Tactile allodynia is monitored over 9 days with classical and electronic von Frey filament tests. Additional endpoint tests can be conducted to enhance the data set:
- Thermal allodynia (plantar test, cold plate)
- Motor capabilities (fine motor kinematic gait analysis)
- Longitudinal imaging of the sciatic nerve area to study inflammation (TSPO-SPECT) and metabolic activation (FDG-PET)
Example study paradigm of the neuritis model for peripheral neuroinflammation. Duration is dependent upon study goals.
Quantitative response to pressure by electronic von Frey filament decreases over time until day 9 in the ipsilateral (left) hind limb. Allodynia can be fully reversed by gabapentin (GP, at day 3). The symptoms return after the washout period (day 7 and 9).
Animals affected with neuritis exhibit significant fine motor movement changes in gait compared to naive rats, as shown by increased hip height in neuritis rats compared to naive rats. (* p<0.001)
Noninvasive imaging enables monitoring of the inflammation and evaluation of the therapeutic over time. FDG-PET (top row) and TSPO-SPECT (bottom row) measurements in neuritis-induced rats show clear activation of tissue metabolic activity as well as inflammation, respectively.