Objective:To evaluate the role of hippocampal β4-Subunit-Containing Nicotinic Acetylcholine Receptors (Chrnb4) in postoperative delirium in aged mice.Methods:Forty-eight SPF male C57BL/6J mice, aged 18 months, weighing 29-35 g, were assigned into 6 groups using a random number table method: tibial fracture group (TF group, n=6), sham operation group (Sham group, n=6), tibial fracture + adipenine group (TA group, n=9), tibial fracture + control vehicle group (TV group, n=9), sham operation + adipenine group (SA group, n=9), and sham operation + control vehicle group (SV group, n=9). The postoperative delirium model was prepared by tibial fracture under sevoflurane anesthesia. Tibial fracture was simulated by implanting a steel pin into the tibia and then clamping it, while sham group only received a longitudinal incision and suture after anesthesia. A microinjection cannula was implanted into the mouse skull at 5 days before developing the model in TA group, TV group, SA group and SV group. Three mice from each group were randomly selected for microelectrode implantation in the hippocampal CA1 area. Starting from 30 min after surgery, adipenine (62.5 nmol/μl) 2 μl was infused into the cerebral ventricle for 7 consecutive days in TA and SA groups, and vehicle (2 μl) was administered instead at a 24-h interval for 7 consecutive days in TV and SV groups. The expression of Chrnb4 mRNA in the hippocampal tissues was detected by real-time quantitative polymerase chain reaction at 24 h after surgery. On the 7th and 8th days after surgery, the open-field test and O-maze experiment were conducted to assess the impulsive-like behavior in TA, TV, SA and SV groups. After the behavioral test, the expression of glial fibrillary acidic protein (GFAP) and vesicular glutamate transporter 1 (Vglut1) in the hippocampal CA1 region was detected by immunofluorescence staining. The local field potentials in the hippocampal CA1 region were recorded during the open field test. Results:The expression of Chrnb4 mRNA in the hippocampal tissues was significantly up-regulated in TF group compared to Sham group ( P<0.05). Compared with TV group, the percentage of central path distance in the open field test and percentage of time spent in the open arms of the O-maze were significantly decreased, the power of β-waves in the CA1 field potentials was decreased, the expression of GFAP and Vglut1 in the hippocampal CA1 region was down-regulated, and the co-staining area of GFAP + and Vglut1 + was decreased in TA group and SV group ( P<0.05). There was no significant difference in each parameter between SA group and SV group ( P>0.05). Conclusions:Hippocampal Chrnb4 may be involved in the mechanism of postoperative delirium in aged mice, and this process may be related to inhibition of neuron excitotoxicity.