A Special Cranial Nucleus (CSF-Contacting Nucleus) in Primates

Area of Science:

• Neuroscience
• Comparative Anatomy

Background:

• A unique CSF-contacting nucleus exists in rat brains, directly interfacing with cerebrospinal fluid (CSF).
• The presence of a similar nucleus in primates has not been previously established.
• Confirming this nucleus in primates is crucial for understanding brain-CSF communication.

Purpose of the Study:

• To investigate the presence and characteristics of a CSF-contacting nucleus in primate brains.
• To establish a structural basis for brain-CSF communication in primates.

Main Methods:

• Cholera toxin B subunit conjugated to horseradish peroxidase (CB-HRP) tracer injected into the lateral ventricle of rhesus monkeys.
• Brain tissue analyzed using confocal and electron microscopy for CB-HRP positive structures.
• Three-dimensional (3D) reconstruction of identified neuron clusters.

Main Results:

• CB-HRP labeling remained within the ventricle, showing no parenchymal leakage.
• A bilateral cluster of CB-HRP positive neurons was consistently found from the midbrain to the fourth ventricle floor.
• 3D reconstruction revealed a "rivet"-like shape for the neuron cluster, with some neuronal processes extending into the ventricle.

Conclusions:

• A CSF-contacting nucleus is present in primate brains, analogous to that found in rats.
• This nucleus is proposed as the XIII pair of cranial nucleus, specialized for brain-CSF communication.
• The finding is significant for understanding organismal innervation and neurohumoral regulation.