ABSTRACT
An ultimate goal of neuroscience is to decipher the principles underlying neuronal information processing at the molecular, cellular, circuit, and system levels. The advent of miniature fluorescence microscopy has furthered the quest by visualizing brain activities and structural dynamics in animals engaged in self-determined behaviors. In this brief review, we summarize recent advances in miniature fluorescence microscopy for neuroscience, focusing mostly on two mainstream solutions - miniature single-photon microscopy, and miniature two-photon microscopy. We discuss their technical advantages and limitations as well as unmet challenges for future improvement. Examples of preliminary applications are also presented to reflect on a new trend of brain imaging in experimental paradigms involving body movements, long and complex protocols, and even disease progression and aging.
ABSTRACT
Monitoring neuronal activity in vivo is critical to understanding the physiological or pathological functions of the brain. Two-photon Ca imaging in vivo using a cranial window and specific neuronal labeling enables real-time, in situ, and long-term imaging of the living brain. Here, we constructed a recombinant rabies virus containing the Ca indicator GCaMP6s along with the fluorescent protein DsRed2 as a baseline reference to ensure GCaMP6s signal reliability. This functional tracer was applied to retrogradely label specific V1-thalamus circuits and detect spontaneous Ca activity in the dendrites of V1 corticothalamic neurons by in vivo two-photon Ca imaging. Notably, we were able to record single-spine spontaneous Ca activity in specific circuits. Distinct spontaneous Ca dynamics in dendrites of V1 corticothalamic neurons were found for different V1-thalamus circuits. Our method can be applied to monitor Ca dynamics in specific input circuits in vivo, and contribute to functional studies of defined neural circuits and the dissection of functional circuit connections.
ABSTRACT
An ultimate goal of neuroscience is to decipher the principles underlying neuronal information processing at the molecular, cellular, circuit, and system levels. The advent of miniature fluorescence microscopy has furthered the quest by visualizing brain activities and structural dynamics in animals engaged in self-determined behaviors. In this brief review, we summarize recent advances in miniature fluorescence microscopy for neuroscience, focusing mostly on two mainstream solutions - miniature single-photon microscopy, and miniature two-photon microscopy. We discuss their technical advantages and limitations as well as unmet challenges for future improvement. Examples of preliminary applications are also presented to reflect on a new trend of brain imaging in experimental paradigms involving body movements, long and complex protocols, and even disease progression and aging.
ABSTRACT
Objective To compare the removal efficiency of γδT cells between cornea and ear skin and develop an alternative method for dynamic monitoring of γδT cells in mouse cornea in vivo using 2-photon laser scanning microscopy.Methods The γδT cells in mouse ear skin were monitored before and after antibody neutralization,and the mice corneas were excised and stained for counting γδT cells at 6 h,12 h,24 h after antibody neutralization by using 2-photon laser scanning microscopy,followed by comparison of the removal efficiency of γδT cells between the cornea and ear skin.Results The γδT cells in normal mouse cornea were often distributed in the limbal epithelium and superficial stromal layer.The irregular morphology of γδT cells in the epithelial layer was often accompanied by protuberances,while the stromal γδT cells were mostly round or oval and the number of cells was approximately 27 ± 4.After antibody neutralization,the number of γδT cells in the cornea of mice gradually decreased,and the number of cells at 6 h,12 h and 24 h was significantly lower than that of before depletion (P =0.03,0.00,0.00),and the removal efficiencies were 48％,78％,and 96％,respectively.The γδT cells in ear skin of the normal mice were ellipse or stellate with cell processes and they were located in epidermal layer,and the cell number was about 60 ± 9.After antibody neutralization,the number of γδT cells were significantly reduced at 6 h,12 h and 24 h compared with before depletion (P =0.000,0.000,0.000) and the removal efficiency were 43％,72％ and 95％,respectively.Conclusion The number of γδT cells in the cornea and ear skin is gradually decreased after antibody neutralization,and their removal efficiency is consistent with time.Therefore,monitoring the γδT cells in the mouse ear skin is an ideal alternative to dynamically monitoring the changes in the number of γδT cells in the cornea in vivo.
ABSTRACT
@#Twophoton microscopy is a new technique which combines laser scanning con-focal microscopy and two-photon excitation technique. Two-photon fluorescence microscopy has the advantages of little light damage, small bleaching area, strong penetrability, high resolution, high fluorescence collection efficiency, and high image contrast. It is suitable for dark field imaging and multi-labeled compound measurement, and has been widely used in small animals in vivo optical imaging, such as research for tumour, gene therapy, stem cells, drug development, spinal cord injury, etc.
ABSTRACT
Damage in the periphery or spinal cord induces maladaptive plastic changes along the somatosensory nervous system from the periphery to the cortex, often leading to chronic pain. Although the role of neural circuit remodeling and structural synaptic plasticity in the 'pain matrix' cortices in chronic pain has been thought as a secondary epiphenomenon to altered nociceptive signaling in the spinal cord, progress in whole brain imaging studies on human patients and animal models has suggested a possibility that plastic changes in cortical neural circuits may actively contribute to chronic pain symptoms. Furthermore, recent development in two-photon microscopy and fluorescence labeling techniques have enabled us to longitudinally trace the structural and functional changes in local circuits, single neurons and even individual synapses in the brain of living animals. These technical advances has started to reveal that cortical structural remodeling following tissue or nerve damage could rapidly occur within days, which are temporally correlated with functional plasticity of cortical circuits as well as the development and maintenance of chronic pain behavior, thereby modifying the previous concept that it takes much longer periods (e.g. months or years). In this review, we discuss the relation of neural circuit plasticity in the 'pain matrix' cortices, such as the anterior cingulate cortex, prefrontal cortex and primary somatosensory cortex, with chronic pain. We also introduce how to apply long-term in vivo two-photon imaging approaches for the study of pathophysiological mechanisms of chronic pain.
Subject(s)
Animals , Humans , Brain , Chronic Pain , Fluorescence , Gyrus Cinguli , Microscopy , Models, Animal , Nervous System , Neuroimaging , Neurons , Plastics , Prefrontal Cortex , Somatosensory Cortex , Spinal Cord , SynapsesABSTRACT
Immune cells (leukocytes or white blood cells) move actively and sensitively based on body conditions. Despite their important role as protectors inside the body, it is difficult to directly observe the spatiotemporal momentum of leukocytes. With advances in imaging technology, the introduction of two-photon microscopy has enabled researchers to look deeper inside tissues in a three-dimensional manner. In observations of immune cell movement along the blood vessel, vascular permeability and innate immune cell movements remain unclear. Here, we describe the neutrophil extravasation cascade, which were observed using a two-photon intravital imaging technique. We also provide evidence for novel mechanisms such as neutrophil body extension and microparticle formation as well as their biological roles during migration.
Subject(s)
Blood Vessels , Capillary Permeability , Cell Movement , Leukocytes , Microscopy , NeutrophilsABSTRACT
Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults. Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity. Although many previous studies have suggested that TLR2 contributes to microglial activation and subsequent pathogenesis following brain tissue injury, it is still unclear whether TLR2 has a role in microglia dynamics in the resting state or in immediate-early reaction to the injury in vivo. By using in vivo two-photon microscopy imaging and Cx3cr1(GFP/+) mouse line, we first monitored the motility of microglial processes (i.e. the rate of extension and retraction) in the somatosensory cortex of living TLR2-KO and WT mice; Microglial processes in TLR2-KO mice show the similar motility to that of WT mice. We further found that microglia rapidly extend their processes to the site of local tissue injury induced by a two-photon laser ablation and that such microglial response to the brain injury was similar between WT and TLR2-KO mice. These results indicate that there are no differences in the behavior of microglial processes between TLR2-KO mice and WT mice when microglia is in the resting state or encounters local injury. Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.