Evaluation Of Neurovascular Function In Mouse Cortex Using Multispectral Optical Imaging After Ischemic Stroke

Objective:To acquire the signal of neuron excitability(neuronal[Ca2+]i fluorescence)and blood oxygen in mouse cortex afrter ischemic stroke,and to clarify the relationship between the change of neurovascular function and the degree of cerebral infarction.Methods:(1)The multispectral optical imaging platform contains multispectral optical imaging system and electrical stimulation system.The components of multispectral optical imaging system are Zoom Stereo Microscope,Charge Coupled Device camera,the part of light source and a linked computer terminal.The component of electrical stimulation system is Model 2100 combination optical isolator and pulse compressor.The green fluorescent-calmodulin protein(rAAV-hSyn-GCaMP6f-WPRE-pA)was injected in a C57BL/6 mouse primary somatosensory cortex(S1HL,hindlimb region)using a mouse brain stereotactic instrument before optical imaging.Then an imaging window was made around the S1HL and electrodes were pricked into mouse left hindlimb.Next,the optical imaging and electrical stimulation were running at the same time to acquire the signal of neuronal[Ca2+]i fluorescence and blood oxygen in mouse cortex.(2)The mouse primary somatosensory cortex(S1HL,hindlimb region)was scanned by the multispectral optical imaging platform before and after ischemic stroke modeling operation respectively.Then several data around the infarction were acquired including neuron excitability(neuronal[Ca2+]i fluorescence),the total hemoglobin concentration and the deoxygenated hemoglobin concentration.The focal ischemic cerebral infarction size was quantitative analyzed by TTC staining.Besides,the mice plasma concentration of TNF-?,IL-6 and H2O2 were measured by enzyme-linked immunosorbent assay(ELISA).And modified neurological severity score(mNSS)was also recorded after mice ischemic stroke.Then an analysis was used on the correlativity between the neurovascular optical signals and three indicators above of the cerebral infarction degree separately.Results:(1)The multispectral optical imaging platform is able to acquire the signals of neuron excitability(neuronal[Ca2+]i fluorescence),the total hemoglobin concentration and the deoxygenated hemoglobin concentration in mouse cortex successfully.(2)The optical signals of neuronal[Ca2+]i fluorescence and blood oxygen around the infarction varied during the period of post ischemic stroke.(3)The optical signal of neuron was correlated to cerebral infarction size,plasma TNF-? concentration and mNSS of mice separately(r1=-0.4411,r2=-0.4493,r3=-0.4036,P<0.05).In addition,the total hemoglobin concentration signal was also correlated to these three indicators above(r4=0.4396,P<0.05).Conclusion:The signals of neuron excitability(neuronal[Ca2+]i fluorescence)and blood oxygen are able to represent the change of neurovascular function,and evaluates the progression of ischemic stroke reliably.