As the control element and processing unit for information, the brain is one of the most important organs in humans. Because it is so complex, many processes in the brain are still unexplored. In their scientific report “Structural and functional connectivity from the dorsomedial hypothalamus to the ventral medulla as a chronological amplifier of sympathetic outflow”, published in the scientific journal Nature, Yosuke Kono et al. investigate the structural and functional connection of the dorsomedial hypothalamus, an area in the forebrain, and the ventral medulla, which is located in the rhomboid brain. Here, the structures of rat brains were studied as a model organism. Measurements were made by tractography, a method to visualize particle fluxes in the cells by color, and by voltage-dependent dyes, which can visualize the membrane potential in the neurons by color. Our M8 microscope was used to scan the tissue sections on which the tractography was subsequently performed.
"Psychological stress activates the hypothalamus, augments the sympathetic nervous output, and elevates blood pressure via excitation of the ventral medullary cardiovascular regions. However, anatomical and functional connectivity from the hypothalamus to the ventral medullary cardiovascular regions has not been fully elucidated. We investigated this issue by tract-tracing and functional imaging in rats. Retrograde tracing revealed the rostral ventrolateral medulla was innervated by neurons in the ipsilateral dorsomedial hypothalamus (DMH). Anterograde tracing showed DMH neurons projected to the ventral medullary cardiovascular regions with axon terminals in contiguity with tyrosine hydroxylase-immunoreactive neurons. By voltage-sensitive dye imaging, dynamics of ventral medullary activation evoked by electrical stimulation of the DMH were analyzed in the diencephalon-lower brainstem-spinal cord preparation of rats. Although the activation of the ventral medulla induced by single pulse stimulation of the DMH was brief, tetanic stimulation caused activation of the DMH sustained into the post-stimulus phase, resulting in delayed recovery. We suggest that prolonged excitation of the DMH, which is triggered by tetanic electrical stimulation and could also be triggered by psychological stress in a real life, induces further prolonged excitation of the medullary cardiovascular networks, and could contribute to the pathological elevation of blood pressure. The connectivity from the DMH to the medullary cardiovascular networks serves as a chronological amplifer of stress-induced sympathetic excitation. This notion will be the anatomical and pathophysiological basis to understand the mechanisms of stress-induced sustained augmentation of sympathetic activity."
What was the M8 used for?
Our M8 microscope was used to scan the tissue sections on which tractography was subsequently performed.
Where can I find the publication?
If you want to read the entire publication, click on this link:
Structural and functional connectivity from the dorsomedial hypothalamus to the ventral medulla as a chronological amplifer of sympathetic outfow
