Effects Of Isoflurane On Cognition And NNOS Expression In The Brain Hippocampus Of Aged Rats

Objective To explore the effects of Isoflurane on learning,memory and the expression of the neuron nitric oxide synthetase(nNOS)in hippocampus of aged rats.Methods To use one-trial passive avoidance response to select 105 good-remembrance 22-month-old SD rats,and then randomly divided them into group contrast(group C,n=50)and group isoflurane(groupⅠ, n=55).The rats in group C only inhaled mixed gas containing 40% oxygen for two hours.The rats in groupⅠwere induced by inhalation of 3%isoflurane,after body-righting reflex disappeared(about 10±2min), we use 1.2%isoflurane to maintain anesthesia for 2 hours.The fraction of inspired oxygen is 40%in the course of anesthesia.We randomly took 5 rats for monitoring vital sign by femoral arteriopuncture in the course of anesthesia.Let the rats naturally wake up after anesthesia.Thirty rats were randomly selected from each group at 24h after stopping oxygen or isoflurane inhalation.Then,we use Y-maze training to carry out the ethology observation.The training time is 3 days.Ten rats were randomly selected from the rests of each group at 24h (group C_24hand group I_24h)and 72h(group C_72hand group I_72h)after stopping oxygen or isoflurane inhalation,anaesthetized intraperitoneally with 0.4%pentobarbital sodium and fixed by perfusion with 4℃4%paraformaldehyde. Obtaining head and postfixing in the same solution for 6h at 4℃,serial coronal sections were cut by a cryostat after dehydrating.Section were carried out immunohistochemistrical reaction to observe changes of nNOS expressions in hippocampus.Results The number of correct reaction in I_24his 10.90±2.09,which is less than 13.53±2.24 in C_24h(P＜0.05);the number of initiative avoidance in I_24his 1.60±0.89,which is less than 2.96±1.43 in C_24h(P＜0.05).The number of correct reaction in I_48his 13.47±2.46,which is less than 16.23±2.22 in C_48h(P＜0.05);the number of initiative avoidance in I_48his 2.27±1.01,which is less than 6.70±1.26 in C_48h(P＜0.05);the total reactive time in I_48his 74.60±10.67 sec,which is more than 59.50±9.76sec in C_48h(P＜0.05).There is no significant difference between I_72hand C_72h in every index.The correct reaction and initiative avoidance rate in groupⅠwere significantly lower than that in group C(P＜0.05).In addition,The intensity of staining and the number of nNOS positive neurons in hippocampus was significantly decreased(P＜0.05)in groupⅠcompared to group C at 24h after stopping oxygen or isoflurane inhalation,and these changes almost recoveried at 72h after the anesthesia.Conclutions Isoflurane anesthesia may result in cognitive impairment and inhibit nNOS expression in hippocampus of aged rats,but it almost recovery at 72h after the anesthesia.