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Browsing by Subject "Optogenetics"

Now showing 1 - 3 of 3
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    Anatomical and Optogenetic Investigations of Periglomerular Sensory Fibers in the Mouse Kidney
    (2022-06) Tyshynsky, Roman
    Though sensory-specific renal denervation has been shown to lower blood pressure in some animal models of hypertension, indicating their importance in the development and maintenance of hypertension, the anatomical distribution and function of sensory renal nerve fibers have not been fully elucidated. Both the anatomical and physiological study of sensory renal nerves have previously focused on sensory nerves innervating the renal pelvis due to their density within the pelvis wall. However, previous studies have described the presence of sensory fibers in the renal cortex but did not quantitatively or functionally investigate this cortical innervation. To begin to address the question of the importance of sensory fibers in the renal cortex, I first used immunohistochemical, and tissue clearing techniques to quantitatively describe the anatomical relationship between sensory fibers and glomeruli. I showed that a majority of mouse renal glomeruli, regardless of their depth within the renal cortex, present with a nearby TRPV1+ or CGRP+ sensory fiber. High-resolution imaging of cleared tissue and three-dimensional distance transformation techniques revealed that sensory fibers travel within a few microns of the Nephrin+ signal of glomerular podocytes and come in close contact with multiple glomeruli that share a common interlobular artery. These anatomical results suggest that periglomerular sensory fibers may function in a mechanosensitive manner to monitor glomerular pressures. To attempt to determine their physiological function, I designed an optogenetic device that was implemented in an anesthetized mouse preparation to measure the effects of optogenetic stimulation of TRPV1+ cortical sensory fibers on cortical blood flow, mean arterial pressure, and renal vascular resistance. Additional experiments validated the ability of this preparation to detect expected changes in these measurements with the subcapsular injection of vasoactive substances, the presence of channelrhodopsin in cortical sensory fibers, the functionality of channelrhodopsin-containing TRPV1+ sensory fibers via optogenetic activation of the baroreflex, and the ability of our chosen light source to penetrate the depth of the renal cortex. Nonetheless, the method used for optogenetic stimulation of TRPV1+ fibers in the mouse renal cortex did not elicit significant changes in cortical blood flow, arterial pressure, or renal vascular resistance from baseline values. These inconclusive results indicate that either the TRPV1+ fibers were never sufficiently stimulated by the delivered light, or that their acute activation does not result in measurable short-term changes in the measured values. Taken together, the discovery of sensory fibers near most glomeruli and currently inconclusive results of a novel attempt to stimulate TRPV1+ cortical sensory fibers in a spatial, temporal, and subtype-specific manner indicates that our understanding of the anatomical distribution and function of sensory renal nerves requires additional investigation. A more thorough understanding of sensory renal nerve anatomy and function will also likely improve treatments for renal nerve-based diseases like hypertension.
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    Optogenetic Investigation into the Role of Cerebellar Interneurons in Social Behavior
    (2021-02) Zhang, Hao
    Appropriate social behavior is vital for survival and developmental success of humans and animals. Impaired social behavior is a common symptom in mental illness. However, the neural basis underlying social behavior is not well understood. The cerebellum is classically recognized to be involved in motor control, but recently there has been an increasing appreciation of its role in cognitive and social functions. Human neuroimaging and postmortem studies have shown that cerebellar abnormalities, particularly in Purkinje neurons, are associated with neuropsychiatric disorders. Research using animal models suggests dysfunction of Purkinje neurons, which conduct the output from the entire cerebellar cortex, can generate abnormal social behavior. Yet, how the cerebellar dysfunction is transformed to global pathogenesis of social deficits remains unknown. In the cerebellar circuitry, the activity of Purkinje neurons is critically regulated by molecular layer interneurons (MLIs). In this study, we applied an optogenetic approach to selectively manipulate the excitability of MLIs using a mouse line with genetically encoded channelrhodopsin. By developing an optical stimulation protocol, we demonstrated that the cerebellum was critical for social recognition, which provides a mechanistic insight for the cerebellum-mediated neuropsychiatric disorders.
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    Principles of Computer Numerical Controlled Machining Applied to Small Research Animal Microsurgical Procedures
    (2017-12) Rynes, Mathew
    The palette of tools available for systems neuroscientists to measure and manipulate the brain during behavioral experiments has exploded in the last decade. Implementing these tools, from electrical to optical sensors require the removal of bone tissue without damage to the underlying brain tissue. This is typically a delicate procedure as the skulls of commonly used inbred mouse strains are very thin (~80-500 μm above the mice dorsal cortex). However, with increasing complexity, these microsurgical procedures have become art forms. It takes many months to become skilled at performing these operations. Automating some of the tissue removal processes would potentially enable more precise procedures to be performed. Here, we introduce the ‘Craniobot’, a microsurgery platform, assembled with off-the- shelf components, that combines automated skull surface profiling with a CNC milling machine to perform a variety of microsurgical procedures in mice. The Craniobot utilizes a low force contact sensor that can accurately measure the surface of the skull across the whole dorsal skull with a precision of 2.4 ± 8.5 µm and this information can be used to perform milling operations with comparable precision. We have used the Craniobot to perform skull thinning, small to large craniotomies, as well as drilling pilot holes for anchoring cranial implants. The system is implemented using open source and customizable machining practices, this approach can be expanded in the future to larger animal models, or for more complex procedures and a more comprehensive part of the pipeline of in vivo neuroscience.