Effects of surgical operation on cognitive function in aged rats after isoflurane anesthesia

Abstract

Objective To investigate the effects of surgical operation on the cognitive function in aged rats after isoflurane anesthesia. Methods Seventy-two aged male SD rats (20 months) weighing 500-600 g were randomly divided into 3 groups (n = 24 each): group C inhaled 30% O_2 for 2 h (control); group I was anesthetized with 1.5% isoflurane in 30% O_2 for 2 h (anesthesia) and group O underwent abdominal operation under 1.5% isoflurane (in 30% O_2) for 2 h (operation). Arterial blood samples were obtained at 0.5, 1 and 2 h of operation for blood gas analysis. Eight animals were killed at 24 h after anesthesia in each group. Their brains were immediately removed for detection of the expression of gene and protein of choline acetyltransferase (CHAT) in hippocampas by RT-PCR and immuno-histochemistry. Cognitive function were assessed by Morris water maze test the day before experiment, and once a day for 6 consecutive days starting from the 1 st postoperative day. Results The ChAT gene and protein expression in hippocampus was significantly decreased, and the the escape latency was significantly prolonged, and the frequency of crossing the original platform and the time of staying at the original platform quadrant were decreased in group 1 and O compaired with group C. Cognitive function became stable at day 4 in group B and C but at day 3 in group A. The ChAT gene and protein expression was significantly lower, and the escape latency was longer and the time of staying at the original platform quadrant was significantly shorter after anesthesia in group O than in group I. Conclusion Surgical operation can aggravate the cognitive dysfunction induced by isoflurane and the mechanism may be related to the injury of cholinergic neurons in hippoeampus. Key words: Surgical procedures,operative; Isofluranee; Cognition disorders