异氟醚对老年大鼠海马突触长时程增强效应的影响

目的：观察异氟醚对老年大鼠海马突触长时程增强(LTP)效应的影响，并探讨其影响老年大鼠认知功能的机制。方法：70只雄性老年SD大鼠，断头后取出海马组织，制备厚400 μm的海马脑片。取35张脑片，随机分为5组(n=7)：对照组、异氟醚0.062 5、0.125 0、0.250 0和0.500 0 mmol/L组。各组脑片分别灌流人工脑脊液(ACSF)、异氟醚0.062 5、0.125
0、0.250 0、0.500 0 mmol/L。采用细胞外微电极记录技术，记录海马脑片CA1区细胞外群体峰电位(PS)的变化。另取35张脑片，随机分为5组(n=7)：LTP组、异氟醚LTP 0.062 5、0.125 0、0.250 0和0.500 0 mmol/L组。各组脑片分别灌流ACSF、异氟醚0.062 5、0.125 0、0.250 0和0.500 0 mmol/L。海马脑片记录PS 30 min后，施以100 Hz的高频强直刺激(HFS)，诱发LTP，观察各组脑片HFS后PS幅值的变化。结果：与对照组比较，异氟醚0.062 5 mmol/L组给药后PS幅值无明显改变(P>0.05)，异氟醚0.125 0、0.250 0和0.500 0 mmol/L组给药后PS幅值明显降低(P<0.01)。LTP组HFS后PS幅值增高，较刺激前增加了(34±11)% (P<0.01)。与LTP组比较，异氟醚LTP 0.062 5、0.125 0、0.250 0和0.500 0 mmol/L组HFS后其PS幅值均明显降低(P<0.01)。结论：异氟醚能够抑制海马LTP的形成而影响老年大鼠的认知功能。

Effect of isoflurane on synaptic long-term potentiation in hippocampal slices of aged rats

Objective To investigate the effect of isoflurane on the synaptic long-term potentiation(LTP)in the CA1area of the aged rat hippocampal slices,and elucidate the mechanisms of the effect of isoflurane on cognitive function in the aged rats.Methods Hippocampal slices(400μm thick)were obtained from the brains of 70male Sprague-Dawley rats that were decapitated.The slices were incubated in artificial cerebrospinal fluid(ACSF)at room temperature for at least 120min before use.Thirty-five slices were randomly divided into 5groups(n=7):control group,isoflurane groups(0.062 5,0.125 0,0.250 0and 0.500 0mmol·L-1).All the slices in each group were perfused with ACSF,isoflurane 0.062 5,0.125 0,0.250 0or 0.500 0mmol·L-1,respectively.The slices in each group were performed to record evoked population spikes(PS)using a extracellular microelectrode recording technique.Another thirty-five slices were randomly divided into 5groups (n=7):LTP group,isoflurane-LTP groups(0.062 5,0.125 0,0.250 0and 0.500 0mmol·L-1).All the slices in each group were perfused with ACSF,isoflurane(0.062 5,0.125 0,0.250 0and 0.500 0mmol·L-1),respectively.PSs were recorded for at least 30min before LTP in each group.For LTP induction,high-frequency stimulation(HFS) conditioning pulses(100Hz/s)were applied to the Schaffer collateral-commissural pathway of hippocampus using a bipolar stimulating electrode.The changes in PS amplitude after HFS were analyzed in each group.Results The PS amplitude of the rat hippocampal slices in isoflurane 0.062 5mmol·L-1 group had no significant difference compared with control group (P>0.05).The PS amplitudes in isoflurane groups (0.125 0,0.250 0and 0.500 0mmol·L-1)were significantly decreased compared with control group(P<0.01).The PS amplitude in LTP group after HFS was significantly increased by(34±11)% compared with that of pre-HFS indicating the successful induction of LTP.Compared with LTP group,the amplitudes of the PS in isoflurane-LTP groups (0.062 5,0.125 0,0.250 0and 0.500 0mmol·L-1)after HFS were decreased significantly (P<0.01). Conclusion The inhibition of LTP induction in hippocampus of the aged rats may contribute to isoflurane-induced deficits in cognitive function of the aged rats.