Optical Imaging Of Bilateral Sensory Response Affected By Cortical Spreading Depression

Cortical spreading depression(CSD)is a continuum consists of mass neuronal depolarization and consequential suppression of neural activity.During its propagation,breakdown of transmembrane ion homeostasis abruptly develops,which is reflected by the deflection of extracellular direct current.After it propagates,spontaneous neural activity is depressed for a long time,which is reflected by the silence of electrocorticogram signal and the absence of stimulus-evoked cortical response.Many research results have confirmed that CSD contributes to the underlying neurological basis of migraine with aura,and may play a negligible role in tissue secondary injury in clinical desease of stoke,subarachnoid hemorrhage and brain trauma.In this thesis we developed a multimodal optical imaging system with the capability of fluorescence correction.Voltage sensitive dye(VSD)stained mice and fluorescent cell-type specific transgenetic mice were used for imaging the propagation of CSD and bilateral sensory response before and after CSD.The main contents and results are listed as follows:(1)A fluorescence-corrected multimodal imaging system is proposed,which combines dual-wavelength intrinsic optical imaging and calcium fluorescence imaging,and can achieve simultaneous monitor of hemoglobin and intracellular calcium concerntration together with correction of the calcium fluorescence.Three kinds of cell-type specific GCa MP6 f transgenetic mice are used to simultaneously monitor hemoglobin and intracellular calcium concerntration during the propagation of CSD.The results show that hemoglobin changes are the same among these transgenetic mice,but amplitude of fluorescence change differ from each other.Though the three phases during CSD are the same in Thy1,Som and Vip mice with the first phase of increasing,the second dropping below the original fluorescence baseline,and the third phase of slowly recovering to baseline level,the amplitude of the first increasing phase are significantly different among different mice.The amplitudes are 201±89%,39±18%,and 14±9% in Thy1,Som and Vip mice respectively.After correction,all relative change of cortical regions decline.Som and Vip mice show significant change after correction while Thy1 mice does not.It seems to be more necessary to correct fluorescence during CSD in Som and Vip mice.Furthermore,relative change in regions of vessels are larger than that of non-vessel regions before correction.The two become the same after correction,which suggestes that fluorescence correction can alleviate the vessel artifact in the change patterns during CSD.(2)Bilateral sensory response under normal physiological status is mapped using VSD imaging and calcium imaging of four cell-type specific transgenetic mice.Bilateral hindlimb or whisker evoked response patterns are acquired and characteristics of the temporal and spatial variation are analyzed.Sensory responses exists in both sides of cortex in VSD imaging and in Thy1,Vglut2 mice.In Som mice,only contralateral cortex to stimuli can be activated whereas the ipsilateral cortex cannot.Neither form of stimulation can stably activate sensory responses in Vip mice.Mice in VSD imaging have the shortest response time,rising time and duration.Thy1 and Vglut2 mice share the same temporal characteristics of bilateral responses.Som and Vip mice show longer response time but shorter duration than both Thy1 and Vglut2 mice.Bilateral activation reigon show little difference among Thy1,Vglut2 and Som mice,however,Thy1 mice has the biggest activation area,Vglut2 mice the second and Som mice the smallest.Spatio-temporal variance of response under hinlimb and whisker stimulation are also compared.Results show that the rising time and duration are shorter under hindlimb stimulation with inner activation region on the contralateral cortex and more localized pattern on the ipsilateral cortex.(3)Dinstinct effect on bilateral sensory response are observed after CSD propagates on the right cortex.For VSD imaging,sensory responses are preserved in the right cortex under ipsilateral hindlimb and cortical surface stimulation whereas it is totally absent under contralateral hindlimb stimulation.For calcium fluorescence imaging,CSD has dinstinct effect on bilateral responses among cell-type specific transgenetic mice.Vglut2 mice show high tolerance to CSD with little change in bilateral responses.Sensory response significantly declines in the CSD-affected cortex while remains unchanged in the unaffected cortex in Thy1 mice.Response in the CSD-affected cortex vanishes in Som mice.Combined with the VSD results,the reason of distinct effect of CSD on different mice is analyzed,that distinct suppression of neuronal components(dendrites or soma)caused by CSD may be responsible for these distinct effect.