Abstract
ObjectiveTo investigate whether the CSF-contacting nucleus receives brainstem and spinal cord projections and to understand the functional significance of these connections.MethodsThe retrograde tracer cholera toxin B subunit (CB) was injected into the CSF-contacting nucleus in Sprague-Dawley rats according the previously reported stereotaxic coordinates. After 7–10 days, these rats were perfused and their brainstem and spinal cord were sliced (thickness, 40 μm) using a freezing microtome. All the sections were subjected to CB immunofluorescence staining. The distribution of CB-positive neuron in different brainstem and spinal cord areas was observed under fluorescence microscope.ResultsThe retrograde labeled CB-positive neurons were found in the midbrain, pons, medulla oblongata, and spinal cord. Four functional areas including one hundred and twelve sub-regions have projections to the CSF-contacting nucleus. However, the density of CB-positive neuron distribution ranged from sparse to dense.ConclusionBased on the connectivity patterns of the CSF-contacting nucleus receives anatomical inputs from the brainstem and spinal cord, we preliminarily conclude and summarize that the CSF-contacting nucleus participates in pain, visceral activity, sleep and arousal, emotion, and drug addiction. The present study firstly illustrates the broad projections of the CSF-contacting nucleus from the brainstem and spinal cord, which implies the complicated functions of the nucleus especially for the unique roles of coordination in neural and body fluids regulation.
Highlights
The cerebrospinal fluid (CSF)-contacting nucleus is a unique nucleus in the brain
The tracer was confined within the boundary of the CSF-contacting nucleus (Figures 1A,B), where the microsyringe needle tract can be seen to be located at the core of the CSF-contacting nucleus
After the retrograde tracer was injected into the CSF-contacting nucleus, it was transported in a retrograde manner along the axons; the neural somata projected from the brainstem and spinal cord can be detected
Summary
The cerebrospinal fluid (CSF)-contacting nucleus is a unique nucleus in the brain It is located within the ventral gray of the lower portion of the aqueduct (Aq) and upper portion of the fourth ventricle (4V) floor (Song et al, 2019). The unique characteristic feature of the CSF-contacting nucleus is that it may be a key structure bridging the nerves and fluids (CSF and plasma). The study of this nucleus is about 30 years after we discovered and named this nucleus. The pathways and mechanisms associated with such biological activities have not been elucidated yet
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