RESUMO
Classical migraine patients experience aura, which is transient neurological deficits associated with cortical spreading depression (CSD), preceding headache attacks. It is not currently understood how a pathological event in cortex can affect peripheral sensory neurons. In this study, we show that cerebrospinal fluid (CSF) flows into the trigeminal ganglion, establishing nonsynaptic signaling between brain and trigeminal cells. After CSD, ~11% of the CSF proteome is altered, with up-regulation of proteins that directly activate receptors in the trigeminal ganglion. CSF collected from animals exposed to CSD activates trigeminal neurons in naïve mice in part by CSF-borne calcitonin gene-related peptide (CGRP). We identify a communication pathway between the central and peripheral nervous system that might explain the relationship between migrainous aura and headache.
Assuntos
Peptídeo Relacionado com Gene de Calcitonina , Depressão Alastrante da Atividade Elétrica Cortical , Transtornos de Enxaqueca , Gânglio Trigeminal , Animais , Camundongos , Peptídeo Relacionado com Gene de Calcitonina/líquido cefalorraquidiano , Peptídeo Relacionado com Gene de Calcitonina/metabolismo , Líquido Cefalorraquidiano/metabolismo , Modelos Animais de Doenças , Transtornos de Enxaqueca/líquido cefalorraquidiano , Transtornos de Enxaqueca/metabolismo , Transtornos de Enxaqueca/fisiopatologia , Proteoma/metabolismo , Transdução de Sinais , Gânglio Trigeminal/metabolismo , Gânglio Trigeminal/fisiopatologiaRESUMO
In bioluminescence imaging (BLI), the biochemical reaction between a substrate and enzyme triggers light emission upon convergence. Unlike fluorescence imaging, BLI does not require excitation. In this protocol, we utilize the high signal-to-background ratio of the reaction between luciferase and its substrate to study the exchange of molecules between blood and cerebrospinal fluid. We outline steps for skull window thinning, cisterna magna infusion, intravascular retro-orbital injection, and imaging. For complete details on the use and execution of this protocol, please refer to Møllgård et al. (2023).1.
Assuntos
Cisterna Magna , Diagnóstico por Imagem , Camundongos , Animais , Luciferases/genética , InjeçõesRESUMO
The central nervous system is lined by meninges, classically known as dura, arachnoid, and pia mater. We show the existence of a fourth meningeal layer that compartmentalizes the subarachnoid space in the mouse and human brain, designated the subarachnoid lymphatic-like membrane (SLYM). SLYM is morpho- and immunophenotypically similar to the mesothelial membrane lining of peripheral organs and body cavities, and it encases blood vessels and harbors immune cells. Functionally, the close apposition of SLYM with the endothelial lining of the meningeal venous sinus permits direct exchange of small solutes between cerebrospinal fluid and venous blood, thus representing the mouse equivalent of the arachnoid granulations. The functional characterization of SLYM provides fundamental insights into brain immune barriers and fluid transport.
Assuntos
Encéfalo , Espaço Subaracnóideo , Animais , Humanos , Camundongos , Dura-Máter/citologia , Dura-Máter/fisiologia , Endotélio/citologia , Endotélio/fisiologia , Espaço Subaracnóideo/citologia , Espaço Subaracnóideo/fisiologia , Epitélio/fisiologia , Encéfalo/anatomia & histologia , Encéfalo/imunologia , Líquido Cefalorraquidiano/fisiologiaRESUMO
Investigation of neural circuits underlying visceral pain is hampered by the difficulty in achieving selective manipulations of individual circuit components. In this study, we adapted a dual AAV approach, used for projection-specific transgene expression in the CNS, to explore the potential for targeted delivery of transgenes to primary afferent neurons innervating visceral organs. Focusing on the extrinsic sensory innervation of the mouse colon, we first characterized the extent of dual transduction following intrathecal delivery of one AAV9 vector and intracolonic delivery of a second AAV9 vector. We found that if the two AAV9 vectors were delivered one week apart, dorsal root ganglion (DRG) neuron transduction by the second vector was greatly diminished. Following delivery of the two viruses on the same day, we observed colocalization of the transgenes in DRG neurons, indicating dual transduction. Next, we delivered intrathecally an AAV9 vector encoding the inhibitory chemogenetic actuator hM4D(Gi) in a Cre-recombinase dependent manner, and on the same day injected an AAV9 vector carrying Cre-recombinase in the colon. DRG expression of hM4D(Gi) was demonstrated at the mRNA and protein level. However, we were unable to demonstrate selective inhibition of visceral nociception following hM4D(Gi) activation. Taken together, these results establish a foundation for development of strategies for targeted transduction of primary afferent neurons for neuromodulation of peripheral neural circuits.