In Vivo Labeling Of Brain Active Neurons In Mouse Fear Conditioning

In vivo labeling of various behavioral activity-related neurons is an important research method to analyze the neural mechanism of brain behavior regulation.CaMPARI(calcium-modulated photoactivatable ratiometric integrator)is a new type of calcium-dependent fluorescent protein,It will undergo a conformational change from green fluorescent protein to red fluorescent protein when the intracellular high Ca2+concentration in the accompany of ultraviolet light irradiation,named photoconversion(PC).So,based on the time adjustability of light control,can the CaMPARI technology be used to mark active neurons in fear conditioning in different brain areas? In order to explore this problem,this paper attempts to use CaMPARI technology to mark the active neurons in the mouse's fear behavior in the hippocampus,amygdala,and prefrontal cortex of the mouse brain.First,while giving foot shocks to mice,simultaneous ultraviolet light stimulation was given,it was found that CaMPARI technology can be used to mark neurons that respond to foot shocks in the hippocampus CA1 brain area.Compared with the normal feeding cages(Homecage),the electric shock of the foot can activate more neurons in the CA1 region of the hippocampus.This experimental result shows that by manipulating ultraviolet light,CaMPARI technology can mark behavioral activityrelated activated neurons in the mouse brain.Further experiments have shown that the use of CaMPARI technology can separately label the active neurons in the mouse amygdala that participate in the acquisition and retrieval processes of contextual fear conditioning(CFC).The results of the study show that whether it is in the basolateral amygdala(BLA)or the central amygdaloid nucleus(CeA),the CaMPARI photoconversion ratio in the process of CFC acquisition is significantly higher than that in the CFC retrieval process.In the both two processes,the CaMPARI photoconversion rate of CeA is higher than that of BLA.Colabeling experiments with c-Fos show that neurons labeled by CaMPARI technology have a certain correlation with neurons with c-Fos expression,and have a lower threshold and higher sensitivity.Finally,we investigated the use of CaMPARI technology to mark the in vivo activity of brain interneurons.During the platform fear behavioral stimulation,the two brain regions,hippocampus CA1 and medial prefrontal cortex(mPFC)were stimulated with ultraviolet light,active PV interneurons were labeled,indicating that CaMPARI can not only label widely Active neurons in each brain area,and can also specifically label the subtypes of active interneurons.The results of this series of experiments show that the use of CaMPARI technology can mark the active neurons in the animal's behavior in vivo.Its main advantage is that it has time controllability,that is,as long as the time when the ultraviolet light is given,the neurons that are activated within a period of time can be marked.It also have the ability to discriminate between different behavioral stimulus intensities and the feasibility of marking specific neuron subtypes.