The Change Of The Memory Function And Expression Of Hippocampus Nicotine Acetylcholine Receptor In Rats After Inhalated Isoflurane

1. BackgroundThe post operative cognitive dysfunction (POCD) is a common complication, it's symptom include visual hallucination, auditory hallucination, changed of emotion,learning and memory impairment,et al. It is still not known that the risk factors of POCD; but generally acknowledge them such as: cardiopulmonary bypass, general anaesthesia, hypoxemia, eld, hypotension, et al, particular eld. The incidence of POCD in the elder is higher than others. But the surely mechanism of POCD are not acknowledge.Isoflurane is a common general anesthetic. Isoflurane influrences the blood pressure, cerebral blood flow, cerebral metabolism, the substance metabolism and the electricity conduction of central nervous system. Previous studies show that isoflurane is one of the important reasons of POCD. Initial study demonstrates that nicotinic acetylcholine receptor plays important in central nervous systems, especially in learning and cognition. Initial study demonstrates that nicotinic acetylcholine receptor decreased in the patients of mild cognitive impairment(MCI) and Alzheimer's disease (AD),2. Objective and MethodFrom all above we guessed that inhaled isoflurane could influrence the memory of rats,and the changed of nicotinic acetylcholine receptor in the hippocampus.So we selected adult and eld rats , partial inhaled isoflurane then others not.Through the ethology, morphology and the molecule expression,we observe the change of rats.3. Result3.1 Animal model and the stabilization detectedWe putted the rats in a bag, adjusted the fresh gas flow and the concentration of isoflurane, detected it to keep the concentration of isoflurane is 1.2% stabilely in 5h.In the process we detected the SPO2 and the arterial partial pressure of oxygen.We discovered the SPO2 were in 97%-100% and he arterial partial pressure of oxygen were in 105-120mmHg.They were the same of rats who were not inhaled.3.2 Trained and detected of Morris water mazeThe latency period of eld rats that inhaled isoflurane in the 3d,4d,5d were longer than other groups,but the platform quadrant swim ratio were in the 3d,4d,there were no differences in other groups.Also there were no differences of the platform crossing frequency in 7d,14d,28d.3.3 Immunohistochemistry of alpha4 nicotinic acetylcholine receptor in hippocampusRats were killed by decapitation,and then cerebrum were embed paraffin. Then the hippocampus section were treated by Immunohistochemistry method.We detected them by Fromowitz method and saw that the masccline cells of eld rats that inhaled isoflurane in 1d decreaseed markedly.3.4 The expression of alpha4 nicotinic acetylcholine receptor in hippocampusThrough method of Western blot,we see that the alpha4 acetylcholine receptor of the adult rats that inhaled isoflurane were not changed , compared with the adult rats who not inhaled.But decreased in the eld rats that inhaled isoflurane in 1d,3d.4. ConclusionInhaled 1.2% isoflurane can influence the memory of the old rats may connect with the expression of alpha4 nicotinic acetylcholine receptor in hippocampus. All above ,we suppose that may be the mechanism of the post operative cognitive dysfunction.