Location of single neurons containing HRP for electron microscopy

Area of Science:

• Neuroscience
• Cell Biology
• Microscopy Techniques

Background:

• Electron microscopy requires precise identification of specific neurons for detailed ultrastructural analysis.
• Horseradish peroxidase (HRP) is a commonly used tracer for neuronal pathway tracing.
• Locating HRP-filled neurons for subsequent ultramicrotomy can be challenging.

Purpose of the Study:

• To describe a reliable technique for identifying single neurons labeled with transported horseradish peroxidase (HRP).
• To facilitate the precise dissection and electron microscopic examination of HRP-injected neurons.
• To improve the accuracy of correlating light microscopic observations with ultrastructural details.

Main Methods:

• Tissue sections reacted for HRP demonstration were cleared in glycerol.
• Darkfield light microscopy was employed to visualize the granular HRP reaction product.
• Accurate drawings were made for guiding microdissection for ultramicrotomy.
• Identification of target neurons within microns of the cutting face of the block.

Main Results:

• The granular HRP reaction product was clearly visualized using darkfield microscopy.
• Accurate drawings enabled precise localization of neurons for dissection.
• The technique allowed for the recovery of target neurons close to the block surface.
• Despite minor distortion, essential cellular morphology, including organelles like neurosecretory granules, remained intact.

Conclusions:

• This method enables efficient identification and localization of single neurons containing transported HRP.
• The technique preserves sufficient cellular morphology for recognizing specific organelles under electron microscopy.
• It provides a valuable tool for ultrastructural studies of neuronal pathways and cellular components.