Neurophysiological Markers for the Acute Pain Model in Rats Under Urethane-induced Anesthesia

Certain neurophysiological mechanisms of pain can be investigated in anesthetized animals, and such a model is potentially useful for the development of pain treatment. Yet, the interference of pain-related neural patterns and anesthesia-related patterns should be understood. Here we studied the interplay between acute pain-induced and urethane-induced EEG activity. We analyzed the activity of the rats somatosensory cortex under urethane-induced anesthesia both before and after introducing a painful stimulus (formalin injection into the left hindlimb). Our analysis of the EEG parameters, such as amplitude, amplitude difference between the left and right hemispheres, and spectral entropy showed significant pain-related effects. The responses to painful stimuli depended on the anesthesia phase. These results are applicable to further research in animal models and to monitoring humans placed under general anesthesia.