Effects of repeated anaesthesia on central cholinergic function in the rat cerebral cortex

Background and objective: General anaesthesia may contribute to postoperative cognitive decline in the elderly. The aim was to determine the effects of repeated pentobarbital anaesthesia throughout life on central cholinergic function in the rat. Methods: Young Lewis rats were randomly allocated to two groups. The anaesthesia group (n = 15) was anaesthetized with pentobarbital 20 mg kg(-1) intraperitoneally at 6, 8.5, 11, 13.5, 16, 18.5, 21 and 23.5 months of age. The control group (n = 12) was treated identically, apart from the anaesthesia. At 26 months of age, the animals were killed and the brain dissected and stored for analysis. Central cholinergic function in the cortex and hippocampus was assessed by measuring [H-3]-epibatidine and [I-125]alpha-bungarotoxin binding to nicotinic receptors and choline acetyltransferase (ChAT) activity. Results: Tissue from nine rats in the anaesthesia group and eight in the control group was available for analysis. There was a significant reduction in alpha-bungarotoxin binding in the anaesthetized compared with the control group in the superior cortex (P < 0.0002) and molecular cortex (P < 0.04). There were no significant differences between the groups for epibatidine binding or ChAT. Conclusions: Repeated anaesthesia in rat reduces central nicotinic cholinergic binding in the cortex. The findings may have implications for postoperative cognitive function studies.