Surgical incision induces learning impairment in mice partially through inhibition of the brain-derived neurotrophic factor signaling pathway in the hippocampus and amygdala

Surgical incision-induced nociception contributes to the occurrence of postoperative cognitive dysfunction (POCD). However, the exact mechanisms involved remain unclear. Brain-derived neurotrophic factor (BDNF) has been demonstrated to improve fear learning ability. Additionally, BDNF expression is influenced by the peripheral nociceptive stimulation. Therefore, we hypothesized that surgical incision-induced nociception may cause learning impairment by inhibiting the BDNF/TrkB signaling pathway. The fear conditioning test, ELISA and Western blot analyses were used to confirm our hypothesis and determine the effect of a plantar incision on the fear learning and the BDNF/TrkB signaling pathway in the hippocampus and amygdala. The freezing times in the context test and the tone test were decreased after the plantar incision. A eutectic mixture of local anesthetics (EMLA) attenuated plantar incision-induced postoperative pain and fear learning impairment. ANA-12, a selective TrkB antagonist, abolished the improvement in fear learning and the activation of the BDNF signaling pathway induced by EMLA. Based on these results, surgical incision-induced postoperative pain, which was attenuated by postoperative analgesia, caused learning impairment in mice partially by inhibiting the BDNF signaling pathway. These findings provide insights into the mechanism underlying surgical incision-induced postoperative cognitive function impairment.